In a challenging market amid an uncertain U.S. economic landscape, identifying long-term, promising investment opportunities becomes a difficult task. Further, to make the investment equation even more challenging, there's election risk, as well, with the 2008 U.S. Presidential election five months away.

Still, risk-adjusted investment opportunities exist. Accordingly, here's a 'Fab Five' that should rank with the best the equity markets have to offer, 3-5 years out.

(Note: Don't buy these stocks if you're interested in a short-term trade of six months or less. These are longer-term investments where the goal is a double-digit, average, annual, total return on equity over 3-5 years.)

Potash (NYSE: POT). Current Price: $212, p/e 47. Revised Stop Loss: $170. Potash remains the best of a very good fertilizer bunch, due to its 20% global market share in the namesake fertilizer. Consider buying POT on a pull-back to $202-203, but keep in mind Potash may not retreat to that level.

Mosaic (NYSE: MOS). Current Price: $132, p/e 40. Revised Stop Loss: $97. Mosaic also is well-positioned in phosphate and crop nutrients. Further, the fact that 66% of its revenue is internationally based is especially appealing, given the U.S. economic slowdown.

Transocean (NYSE: RIG). Current Price: $144, p/e 10. Revised Stop Loss: $110. RIG offers deepwater oil drilling services in all regions of the world, and it's an oil-thirsty world.

Freeport-McMoRan (NYSE: FCX). Current Price: $114, p/e 14. Revised Stop Loss: $69. Copper / gold / molybdenum miner Freeport is one of a handful of companies that have the economies of scale to compete in the global mining sector of the early 21st century, and it boasts impressive clients, to boot. Consider buying FCX on a pull-back to $111-113, but keep in mind Freeport may not retreat to that level.

CSX Corp. (NYSE: CSX). Current Price: $66, p/e 23. Revised Stop Loss: $48. Ride the railroad resurgence with this superior trade / commodity / freight transport company. The rails are in the transportation sweet spot: truck transport costs are rising with fuel costs, and the U.S. highway system is inadequate, with increased congestion likely, pending future investment.

Top Pick: Potash.

Safest Pick: CSX Corp.

Disclosure: Lazzaro has no positions in stocks. In addition to private real estate holdings, he owns corporate and municipal bonds, and cash certificates of deposit.

Readers of this space know that one of my preferred sectors is the railroad sector. The growth in international trade, the importance of commodity transport, and record-high oil prices mean the rails will play a central role in the nation's economy. And a railroad stock worth owning is CSX Corp.

CSX Corp (NYSE: CSX) operates the largest rail network in the eastern United States, with a 22,000-mile rail network in 23 states and two Canadian provinces.

In general, analysts see 9-12% revenue growth for both 2008 and 2009, with continued pricing power (including expired contract re-pricings) and improved asset utilization.

Further, coal traffic should rebound in 2008, while intermodal traffic is expect to remain solid, even with a slowdown in the building materials and automotive businesses.

Also, several infrastructure improvements and capacity increases should improve CSX's delivery times and reduce dwell times. The Reuters F2008/F2009 EPS consensus estimates for CSX are $3.60/$4.23.

Currently trading around $68 with a p/e of 226, CSX is not cheap. But the view here is that the 3-5 year outlook is promising for this major rail line; moreover, the likelihood of persistently-high oil prices means more businesses will switch to rail transport for goods.

When a major, metropolitan U.S. newspaper discovers a investment trend or a hot sector, count on increased share demand for companies in the sector. When that paper is one of the top three dailies, in this case The Washington Post, count on even more demand.

On Monday, The Washington Post examined the resurgence of the United States' railroad sector, touching on many of the themes discussed here during the past six months, and described why the rails' services are likely to be in demand for many years.

Readers of this space know that the preference here is for large cap companies, with demonstrated business models, and favorable long-term factors, that have the resources to ride-out short-term economic downturns, including recessions.

And in this category a railroad stock represent a prudent addition to a portfolio, for investors who can tolerate moderate risk.

Pick a railroad. Virtually any railroad. Odds are, you will do fine, long-term, as the nation continues to re-discover the valuable asset - - the national treasury, really - - of its railroads. (More on that latter topic, in a future blog.)

Here are the railroad plays, ranked by risk, with the top stock, BNI, being the lowest risk. A stop/loss, if one were to buy the stock, is also listed:

Way back in the 20th century, rails were hardly considered a growth play. But with consistent demand for commodities and raw materials, along with the (seemingly) continual rise in truck transport costs, the rails are becoming a primary shipment mode, which means good things -- long-term -- for rail companies.

Among the rails, CSX Corp (NYSE: CSX) is a company worth a review. CSX operates the largest rail network in the eastern United States, with a 22,000-mile network in 23 states and two Canadian provinces.

In general, analysts see CSX's revenue growth slowing somewhat in 2007, offset by better margins, pricing power (including expired contracts repricing) and improved asset utilization.

Further, coal traffic may slow heading into 2008, but intermodal traffic is expected to remain solid. Numerous infrastructure improvements and capacity increases should improve CSX's delivery times and reduce dwell times. In addition, trading around $42 with a p/e of 16, CSX currently is somewhat of a bargain, as Wall Street has discounted CSX's share for a U.S. economic slowdown, taking the stock down about 20% from a $52-high reached this summer.