"Railroads are a play on three big secular themes: the drive for increased energy efficiency, growth in coal and the agriculture boom," says Elliott Gue, a energy sector expert who has just returned from Japan where he was covering the G8 Summit.

Meanwhile, in his The Energy Srategist, he states, "Railroads are now among the most fuel-efficient forms of freight transport available." Here, he offers a bullish review of Union Pacific (NYSE: UNP).

"My long-held thesis on the group has been that the railroads are no longer totally dependent on the US economy for their growth.

"It's no longer appropriate to look at this sector as viciously economy sensitive. The traditional relationship between the broader market and the rails has been breaking down for several years, but this trend appears to be accelerating.

"In 2007, according to the Association of American Railroads (AAR), the average railroad moved a ton of freight a distance of 436 miles on a single gallon of diesel fuel. That makes freight trains roughly three to four times more fuel efficient than trucks.

"Union Pacific is the largest railroad in the US and has long been one of my favorites. The company's network is nearly 33,000 miles long and is concentrated in the West and Midwest. It also offers a convenient example of the bullish forces at work for the rails, particularly in the coal and agriculture industries.

"As steel prices continue to climb, one company that is set to profit handsomely is Cleveland-Cliffs (NYSE: CLF)," says Bill Martin.

Adding to the stock's appeal, the editor of BullMarket.com explains, "Event-driven hedge fund Harbinger Capital has been an aggressive buyer of the stock." Here's his review of the situation.

"Shares of Cleveland-Cliffs have been on fire, up over 150% year over year and they have more than doubled year to date. The Cleveland, Ohio-based company is the largest producer of iron ore pellets in North America and a major supplier of metallurgical coal to the global steel-making industry.

"Cleveland-Cliffs benchmarks iron ore prices to the price of steel, so when steel prices rise, so do iron ore prices. The company said all of its North American iron ore mines are producing at or near capacity.

"Cleveland-Cliffs ended the first quarter of 2008 with $186.5 million of cash and cash equivalents and $600 million in borrowings outstanding under an $800 million credit facility. The company expects to generate approximately $700 million in cash from operations in FY08 as it sells through its inventory.

"Event-driven hedge fund Harbinger Capital was an aggressive buyer of the stock in May, paying between $76.96 to $104.75 a share to add to its position in the name. For the month, the firm spent approximately $338.5 million to acquire nearly 3.7 million shares.

"The number one reason I like gold is because of inflation -- now a big problem in the emerging markets and the major economies," says resource expert Eric Roseman.

In his industry-leading Commodity Trend Alert, he says, "One of my favorite companies in the world is Goldcorp (NYSE: GG)." Here, he looks at this gold mining firm.

"Inflation sits at a nine-and-a-half-year high in Asia at 7.5%, a 15-year high in the Euro-zone at 3.7% and in the United States it's at 4.2% -- if you believe government data in the first place. I don't. I say inflation is running closer to 10% in 2008, not 4.2%.

"The cost of living, mainly in food and energy, is now totally out of control and destroying business margins and eroding the purchasing power of consumers, especially in the emerging markets where food and energy consumption devours more than 65% of wages.

"It seems very obvious to me that Asian governments have now lost control of inflation. The same applies to the Gulf countries which peg their currencies to the dollar. And in Europe, the European Central Bank is freaking out because of high inflation.

Although he has been maintaining a cautious stance on the refining group, energy sector expert Elliott Gue is now boosting the rating on Valero Energy (NYSE: VLO).

In his The Energy Strategist, the advisor explains, "Valero is now attractive for three reasons: superior geographic exposure, refinery complexity and a new focus on profitability."

"Our caution on the refining group was due to expectations that crack spreads would be weak through the spring, a period during which spreads tend to widen. Overall, this call was correct: Refiners have underperformed the energy patch since mid-March.

"And longer term, I have some concerns about new refining capacity expansions due to come online over the next few years. As this supply comes online, it could put downside pressure on margins.

"But over the next six to nine months, the refiners look like a compelling play. Gasoline inventories are now back in line with seasonal norms; it's likely gasoline prices will now rally further relative to crude oil. In fact, we're already seeing an obvious spike in crack spreads.

"I think that the most compelling stocks are the dry bulk shippers," says Charles Payne. In his Wall Street Market Commentary, he looks at the sector, its implications for the economy and his favorite picks.

"The dry bulk shipping group had been under a fair amount of pressure after a meteoric rally that said rates would come on with a Tiger Woods-like rebound after swooning at the start of the year.

"I consider the dry bulk index the best barometer of the health of the global economy. There is no doubt that at some point higher crude oil becomes the headwind everyone says it is, but I'm still not sure that level has been reached yet.

"On the global stage, many nations are paying substantially more for gasoline than the U.S. and yet their economies continue to improve. Obviously, on the one hand we would like crude oil to respond to a demand tipping point by way of Americans saying 'no mas.'

"By the same token; however, it would also be encouraging to know/see the economy getting better even in the face of this would-be headwind. I have to say that recent slide in dry bulk rates could be more technical rather than some sort of reaction to higher crude oil; the long-term trend is intact and today's action is compelling.

"Our favorites in the group include Genco Shipping (NYSE: GNK) which looks great in current trading, Teekay Shipping (NYSE: TK), and Diana Shipping (NYSE: DSX). All of these stocks are oversold and have tremendous room on the upside."

Each day, Steven Halpern's TheStockAdvisors.com offers the latest market commentary and favorite investment ideas from the nation's leading financial newsletter advisors.

"Potash (NYSE: POT) scored a technical breakout by rising above $210," says technical expert Leo Fasciocco. In his Ticker Tape Digest, he says, "With earnings set to soar the stock now targets a move to $265."

"Postash, based in Canada, produces fertilizer. It produces phosphate and nitrogen from 12 facilities in the United States and South America. Fertilizer stocks have been strong due to rising profits reflecting strong demand for their products and rising prices.

"A long term chart shows an extraordinary bull market advance with the rising 170% the past 12 months versus an 8% decline in the S&P 500 index. Now, the stock has broken out from a seven-week flat base. The move carries POT to a new high on expanding volume.

Leo Fasciocco is a technical expert who focuses exclusively on finding breakout candidates. In his Ticker Tape Digest, he looks to agriculture equipment manufacturer Deere & Co. (NYSE: DE).

"Deere, with annual revenues of $24.8 billion, makes agricultural, industrial, forestry, and lawn-care equipment. DE is benefiting from the strong demand for its products in the farm sector. The company is also expanding aggressively in Russia.

"DE has broken out from a 13-week flat base. Its long-term chart shows DE soaring from 20 in 2003 - the start of the prior bull market - to 92. It has been a big winner in the big cap sector. The stock has gained 65% in the past 12 months versus a 5% drop in the S&P 500 index.

"The stock is in a base bracketed between roughly 78 on the downside and 91 on the upside. The breakpoint was set at the key upside resistance of the base. Deere has plowed through that resistance on increasing volume.

"Green investing and clean energy may be the politically correct topic at cocktail parties, but coal is the economically correct vehicle for investors," says Ronald Rowland and Brandon Clay.

The editors of All Star Investor explain, "Coal has been an energy source for millennia -- and is still the number #1 source of energy for electric power plants in the world." And, they add, "One of the best places to invest in coal is Consol Energy (NYSE: CNX).

"Prehistoric Chinese are said to have used coal for heating. According to Roman historians, Britain burned coal in the first century. Throughout history, coal has been the primary source of heat in homes.

"Rapidly industrializing nations like China are still dependent upon coal for energy. Overall global consumption has not diminished either. Coal fuels 48% of electricity plant generators. And the trend is heading upward – probably for the next 30 years. Despite the deafening rhetoric, coal is not going away anytime soon. Investors should take notice.

"We're adding a position in one of our favorite ETFs for 2008: the PowerShares DB Agriculture Fund (NYSE: DBA), which provides investors with an alternative way to invest in the agricultural sector," says technical analyst and contrarian investor Chris Johnson.

The money manager and editor of Insightful Investor explains, "We feel a long-term position in DBA is appropriate for any investor's portfolio." Here is his review.

"One of the areas of the economy that we have been outwardly bullish on is the agricultural group. From a fundamental perspective, the 'ag play' is in full force, as demand and supply remain imbalanced. This has been a fantastic catalyst for a number of stocks that have to do with the agriculture sector, as we have heard in the news quite a bit lately.

"While we like the environment that this creates for a number of stocks, there is one agricultural investment that we do not hear trumpeted in the media as much as one might expect. We're referring to an investment in agricultural products, not the companies that help to produce the products.

For 25 years, Steven Halpern, editor of TheStockAdvisors.com, has surveyed the leading financial newsletter advisors asking for their favorite stocks for the coming year. This article is one of 100+ ideas in the Best Stocks for 2008 report.

"If you are looking for a quality company paying an outstanding dividend with excellent upside potential, I recommend Terra Nitrogen (NYSE: TNH), my top conservative selection for 2008," says Dennis Slothower, editor of Stealth Stocks.

"The company produces and distributes nitrogen fertilizer products, used primarily by farmers to improve yield and quality of their crops. With the trend toward bio-fuels, the demand for nitrogen fertilizers has an exponential future.

"The company is one of the largest North American producers of anhydrous ammonia, ammonium nitrate and nitrogen solutions, and is the largest producer of ammonia and ammonium nitrate in the United Kingdom.

"I like this stock for several reasons. It pays a very handsome dividend of 7%, but this is also a growth company that is undervalued with a P/E ratio of 12 times earnings but a sales growth rate of 45%.

"The intrinsic value of this stock is $235 a share. This has the potential of doubling or even tripling your investment over the next three to five years while paying an excellent dividend."

For 25 years, Steven Halpern, editor of TheStockAdvisors.com, has surveyed the leading financial newsletter advisors asking for their favorite stocks for the coming year. This article is one of 100+ ideas in the Best Stocks for 2008 report.

"Mechel OAO (NYSE: MTL), Russia's second-largest producer of long steel products," is our favorite speculative play for 2008," say co-editors Roger Conrad and Yiannis Mostrous in Vital Resource Investor.

"The company operates one major steel mill with a capacity of close to 5 million tons of output per year. Mechel operates in Russia, Lithuania and other countries in Central and Eastern Europe. Its ace in the hole is a mining business that focuses on raw materials used in making steel, primarily coking coal, iron ore, nickel and steam coal.

"The company's steel business is 100% self-sufficient in coking coal, 80% in iron ore and 50% in electricity. This aspect of Mechel (i.e., vertical integration) is critical in an environment where raw material prices continue to rise. And it should support the stock because its performance this year has been nothing less than dazzling.

"Mechel is a high-cost producer, and management has worked to cut costs while improving efficiency. Those efforts have been quietly successful up to now, and we expect this to be an ongoing positive theme.

"And Russia's strong domestic demand -- within and outside the all-important energy sector -- is an additional advantage for the company. Buy Mechel at current prices."

For 25 years, Steven Halpern, editor of TheStockAdvisors.com, has surveyed the leading financial newsletter advisors asking for their favorite stocks for the coming year. This article is one of 100+ ideas in the Best Stocks for 2008 report.

"Everyone should have some gold, but it is an individual decision as to what best fits one's risk tolerance and personal financial makeup," says resources expert Curtis Hesler, editor of Professional Timing Service.

"Bullion in some form, be it bullion coins or bullion ETF's like StreetTracks Gold ETF (NYSE: GLD), should be fitted into one's portfolio -- for diversification, if no other reason. I would consider this a top speculative idea for 2008.

"However, be mindful that bullion profits, even in the ETF form, are taxed at a higher rate than gold-mining stocks. So, bullion ETF's are perhaps best held in a tax-sheltered account, but that is an individual call."

For 25 years, Steven Halpern, editor of TheStockAdvisors.com, has surveyed the leading financial newsletter advisors asking for their favorite stocks for the coming year. This article is one of 100+ ideas in the Best Stocks for 2008 report.

"The momentum for large-cap gold producers looks very bullish and my top speculative idea for 2008 is Yamana Gold (NYSE: AUY)," says Eric Roseman, editor of Commodity Trend Alert.

"Based in Toronto, Canada, Yamana is a large-cap gold-mining company with probably the best exploration portfolio in all of Central and South America.

"Yamana Gold had been heavily battered due to its buyout of Meridian Gold and Northern Orion. With these acquisitions now completed, the overhang of merger uncertainty has been lifted and the stock has sharply rallied off its 52-week low.

"The big picture for Yamana is a great portfolio of first-rate mines in Central and South America, booming earnings, rising positive cash-flow and production costs of $339 per ounce.

If you could buy only one commodity stock, what should it be? Mary Anne and Pamela Aden, long-standing experts in the natural resources sector, think that one stock should be BHP Billiton (NYSE: BHP).

The editors of The Aden Forecast explain, "The hot Asian markets are keeping demand strong for commodities. Indeed, the commodity move has been gearing up, one by one. Some markets will be stronger than others at times, but they are all in a major rise with demand being the driving force, which makes this mega move even more powerful."

The advisors continue, "China and Asia in general have been booming for many years now. The slowing economy in the U.S. caused concern that the fiery growth in Asia would cool down. It certainly could with time, but so far there are no signs of this at all."

Meanwhile, they notes, demand for raw materials remains and 2007 may end up seeing China's economy expand at the fastest pace in 12 years. To benefit from this trend, the sisters says, "BHP Billiton has long been one of our favorites because it's the best way to stay invested in the whole raw materials sector."

They notes that Billiton is the world's largest mining organization, stating, "It's a leader in steel making, it's the world's third largest producer of copper and nickel, second largest exporter of coal, fourth largest producer of uranium... and the list goes on." They conclude, "So if you have to buy just one natural resource company, let it be BHP."

Each day, Steven Halpern's TheStockAdvisors.com features the latest investment ideas and market commentary from the financial newsletter community.

The New York Times recently made a case for investing in stocks to gain exposure to commodities:

But there is an easy way to get a shot at commodity-like returns, without investing directly in commodities or their indexes. Investors can buy shares of the natural resource companies that produce commodities.

However, investors need to be careful: just because a stock is in a sector related to commodities doesn't mean that it will move with the prices of those commodities. Other factors, including decisions by management, any hedging the company may have in place, and other company-specific factors, may cause their returns to differ from those of the underlying commodities. While it's quite true that, as the New York Times points out, natural resources stocks have outperformed commodities in recent years, that is not a trend that will necessarily continue.

There may be good reasons to buy these stocks, but if you want to make a bet on commodities prices, the best way to do that is with exchange-traded funds (ETFs). Back in his days at the Motley Fool, BloggingStocks contributor (who is the source for news and analysis for private equity, by the way) Tom Taulli wrote a nice piece about how to invest in commodities through ETFs.

If you really want to learn about ETFs, I recommend picking up a copy of Investing with Exchange-Traded Funds Made Easy: Higher Returns with Lower Costs -- Do It Yourself Strategies without Paying Fund Managers by Marvin Appel.