Dragged down by the challenging market conditions, many stocks have fallen under $10 lately. CNBC's Cindy Perman suggests that some of these stocks could be become good investments for traders. However, not everything that is cheap could be such a good bargain, Perman reminds us. You must always do your homework on potential investment before buying.

For example, Ford Motor (NYSE: F) fell down to around $6 compared with $38 nine years ago -- is it a good investment? Well, while the automaker revealed its plans to shift production from trucks to cars and give a boost to its turnaround plan, it also warned it won't be profitable until 2010 at the earliest.

Perman quotes several investment specialists on the matter. John Schloegel, vice president of investment strategies at Capital Cities Asset Management says, "An investment in Ford today feels like being in the wrong place at the wrong time." And Greg Womack, president of Womack Investment Advisers, advices to stay away from the sector, which doesn't look promising now, for the next three to five years to find out the "winner."

MOST NOTEWORTHY: Schering-Plough, Emergency Medical Services and SLM Corp were today's noteworthy upgrades:

• Banc of America upgraded shares of Schering-Plough (NYSE: SGP) to Buy from Neutral on valuation, as they believe current levels already reflect significant cuts to the company's cholesterol franchise from ENHANCE.
  
• JP Morgan upgraded shares of Emergency Medical Services (NYSE: EMS) to Overweight from Neutral following the company's Q4 results.
  
• Friedman Billings upgraded shares of SLM Corp. (NYSE: SLM) to Outperform from Market Perform and raised their target to $25 from $23 to reflect the company's strengthened capital position, diversified sources of income, and attractive valuation.

OTHER UPGRADES:

• JP Morgan added Molson Coors (NYSE: TAP) to its Focus List.
  
• Citigroup raised Dynegy (NYSE: DYN) to Buy from Hold.
  
• Societe Generale upgraded Credit Suisse (NYSE: CS) to Hold from Sell.

MOST NOTEWORTHY: Infosys Technologies, Cognizant and Ansys and were today's noteworthy initiations:

• Infosys Technologies (NASDAQ: INFY) was initiated with a Buy rating and $54 target at Kaufman, as their checks indicate no signs of a slowdown in the Indian software services market. They believe the stock is getting no premium for its defensive nature.
  
• Kaufman also initiated Cognizant (NASDAQ: CTSH) with a Hold rating and $35 target and believes the company's less defensive revenue mix could cause its P/E multiple to trend below rivals.
  
• Ansys (NASDAQ: ANSS) was initiated with a Hold rating and $39 target at Jefferies. The firm recommends waiting for a better entry point given the peak operating margins, a more challenging macro backdrop and tougher comps.

OTHER INITIATIONS:

• Wachovia initiated Invesco (NYSE: IVZ) with a Market Perform rating.
  
• Dynegy (NYSE: DYN) was assumed with a Buy rating and $9.50 target at Merrill.
  
• Navios Maritime (NYSE: NMM) was started with an Overweight rating at JP Morgan.

MOST NOTEWORTHY: Catalyst Pharm, Ruth's Chris Steak House and Dynegy were today's noteworthy initiations:

• Rodman & Renshaw is optimistic on Catalyst Pharmaceutical Partners' (NASDAQ: CPRX) Vigabatrin in drug addiction, initiating shares with a Market Outperform rating and $9 target.
• SunTrust started Ruth's Chris Steak House (NASDAQ: RUTH) with a Neutral rating and $13 target, citing the difficult spending environment and cautious sentiment.
• Jefferies initiated shares of Dynegy Inc. (NYSE: DYN) with a Buy rating and $9 target and expects improved cash flow and earnings from the projected improvement in market heat rates in the Midwest and PJM.

OTHER INITIATIONS:

• Bear Stearns resumed coverage of Siemens AG (NYSE: SI) with an Outperform rating.
• Wachovia initiated the pharmaceutical services sector with an Overweight rating and started Covance Inc. (NYSE: CVD), Icon plc (NASDAQ: ICLR) and Kendle International (NASDAQ: KNDL) with Outperform ratings.

The historical trade-off between the price of oil and natural gas has been 6 to 1, meaning if oil sold for $30 per barrel and natural gas for $5 per mmcf, the two commodities would be equally priced on a BTU basis.

Therefore, a natural substitution effect occurs. When oil is greater than six times the price of natural gas, it would be cheaper for consumers of energy to substitute gas for oil. Conversely, if oil were less the six times the price of natural gas, it would be cheaper to use oil and switch away from using gas. This substitution effect pretty much kept this ratio in tact.

However, in today's market, with oil at $82 per barrel and natural gas selling for $6.00 per mmcf, that ratio has expanded to 13.6x (!). That's huge. This means consumers of energy should be switching all their energy consumption away from oil to natural gas.

How should investors play this? One way is to short oil and go long natural gas. However, that could prove to be a risky strategy. Another way is to look at merchant power producers that use natural gas. Two plays are The AES Corporation (NYSE: AES) and Dynegy Inc (NYSE: DYN). Both use a good amount of gas to produce power and both have corrected rather meaningfully during this market downturn and represent good value.

The Washington Post reports that pension fund managers representing $1 trillion have petitioned the Securities and Exchange Commission (SEC) to required public companies to disclose the impact of global warming on their business prospects. If the SEC agrees, the change could threaten investors in utility stocks -- which are among the biggest private sources of carbon dioxide emissions that cause global warming.

Here's a list of utility stocks which could be most affected:

• American Electric Power (NYSE: AEP). AEP produced 145.4 million tons of carbon dioxide in 2006. In Europe, where legislation already limits carbon dioxide emissions, allowances for a ton of carbon dioxide sell or 20.5 euros, or about $28.50. So if its 2006 carbon dioxide had been emitted in Europe, AEP would have had to pay over $4 billion.
• Dominion Resources (NYSE: D)
• Dynegy (NYSE: DYN)
• Xcel Energy (NYSE: XEL)

Coal producer, Peabody Energy Corp. (NYSE: BTU) could also be among those companies affected.

Broader credit market worries sacked stock futures Thursday after French banking group BNP Paribas suspended three funds -- tying up client investments -- saying it could not accurately value them due to a lack of liquidity throughout the U.S. securities market. The news sent U.S. bank stocks lower overseas.

The Dow is poised to retreat after padding the week's gains by 153.56 in Wednesday's trading. The Dow has climbed nearly 475 points since Friday's 281-point plunge.

Companies reporting earnings Thursday include HealthSouth Corp. (NYSE: HLS) and Dynegy Inc. (NYSE: DYN).

The Labor Department will give its weekly report on new unemployment claims at 8:30 a.m.

The Nikkei rose 1 percent to 17,240.99, pushed higher on news that Barneys New York has passed on a buyout bid from Japan's Fast Retailing. The FTSE 100 rose 1.33%.

In overseas currency markets, the dollar gained 0.3% on the euro, but slipped 0.7% against the yen.

Company news

AIG (NYSE: AIG) posted unexpectedly high income in its second-quarter report Wednesday, but cited cramping from weakness in the housing market.

News Corp, (NYSE: NWS) fresh off its successful bid for Dow Jones, reported higher profits over last year's fourth quarter.

Online search provider Infospace Inc. (NYSE: INSP) slipped overseas after reporting losses of 86 cents per share -- far worse than analysts' expectations of 12-cent losses.

Power generation stocks, such as Dynegy Inc (NYSE: DYN) and AES Corporation (NYSE: AES), have gotten beaten up pretty good the past few weeks. We blogged recently about the merits of jumping into AES. But Dynegy is another company that investors should look into after the recent market weakness.

As we blogged yesterday, investors should look at sectors that got hit hard in the tech-telecom bubble, as scars in these sectors run deep and investors are quick to run for the hills even though industry fundamentals are much improved. The same can be said for the power generation business.

The power generation business, particularly the merchant power producers, went through a similar type of bust cycle as the telecom sector, with many companies entering bankruptcy. However, Dynegy, which was a must-own stock along with Enron in the late 1990s, was able to avoid bankruptcy, bring in new management, dispose of its money losing tolling arrangement and recently made a large acquisition of a privately held power generator which will help it to grow.

Management in Dynegy is top notch, having come from Duke Power, and has executed magnificently to turn this company around and turn it into an important player in the power generation business. This is one stock your want to consider for your buy list on this market correction.

As a follow up to my blog yesterday, here are a few other ideas to look at as this stock market correction continues to unfold.

Newell Rubbermaid Inc (NYSE: NWL), a stock we have blogged about the merits of repeatedly during the past year, is holding up steady. There are a couple of reasons for this -- first, Newell, as a consumer staple company, attracts money during volatile markets, and second, the belief that its turnaround is for real.

Dynegy Inc (NYSE: DYN) is also holding up well. Similar to the IP transport companies blogged about yesterday, this stock typically got hit hard during these market corrections during the past few years. However, in this selloff, it has declined little. With private equity firms eyeing TXU, investors are beginning to believe in the merchant power business again.

Use this correction and current bout with fear to pick up some good stocks. Newell and Dynegy are companies to throw into your portfolio.