There are three areas of the market that I've been scouring for undervalued stocks recently: banks, oil, and small caps. Why these three in particular? Here's my rationale for each (as well as some specific stock ideas).

Banks
The banking sector may be the most complex, opaque market segment. Derivatives, accounting quirks, deleveraging, and government intervention make this so. As a result, there is a lot of opportunity out there for those who can parse out the winners. But just because there is opportunity doesn't mean it's a good idea to make individual calls in the sector.

I've written before about the dangers inherent in the sector. Bank of America and Citigroup (NYSE: C) are popular because they were left for dead at one point. They've recovered somewhat from a price standpoint -- leading to multibaggers off the lows -- but they still share the complexity problem with their stronger peers including Wells Fargo , Goldman Sachs , and JPMorgan Chase . All of these banks either have significant investment banking operations or have swallowed up a fallen toxic bank.

I see more opportunity in the smaller, simpler banks. I detailed my thoughts a few months agoand later bought into one of my research candidates, Community Bank System .

Oil
I chose oil specifically rather than the energy sector as a whole because I feel more confident in buying into an oil major like BP (NYSE: BP) than I do an alternative energy player like Suntech Power Holdings (NYSE: STP). The gains in alternative energy could indeed be huge, but similar to the slew of Internet companies in the late '90s, it's exceedingly difficult to separate the rare Amazon.com 's (Nasdaq: AMZN) from the many losers.

Even with the alternative energy threats, our dependency on oil should exist for quite a while. The opportunity for large gains comes in buying oil companies (from the little guys like Dawson Geophysical to the ExxonMobil s of the world) on weakness -- specifically when there's oil price weakness. I first wrote about thisback in the spring when oil was closer to $50 a barrel. There may be good opportunities now, but if oil falls back into the 40s and 50s, and oil stocks weaken, definitely do your research and consider seizing the opportunity.

Small caps
There are certainly bank and oil small caps that are worth researching (I mentioned a bank example already) if you have the requisite expertise. But small caps (i.e., companies with market capitalizations between $200 million and $2 billion) span every sector out there, so if banks and oil aren't your thing, you can tailor your search to your circle of competence.

Small caps tend to be more volatile than their larger brethren, so when the stock market experiences turbulence (read: now!), small caps experience earthquake-like movement.

When the price is right, we can capitalize.

Let me walk you through a screen I'm using to find promising small caps. It's a little boring, but stick with me, because there are some interesting stocks at the end.

I'm not interested in temporary beauty, so I looked for companies that had both positive earnings and positive free cash flow for the last five years. For cheapness' sake, I also made sure the companies were trading for less than 10 times the most recent earnings and free cash flow numbers via the P/E and P/FCF metrics. A lot of wonks bicker over whether P/E or P/FCF is a better metric. Frankly, I see no reason why both earnings and cash flow shouldn't be strong -- we want companies that are both accounting profitable andgenerating cash off of that profitability. As a final check, I made sure the companies were easily able to cover their interest payments.

The screen generated 17 companies, but one in particular caught my eye. Here's the complete list: 

Company

P/E Ratio

P/FCF Ratio

Terra Nitrogen (NYSE: TNH)

9.9

9.4

Gentiva Health Services

4.4

8.7

EarthLink

6.0

7.9

Suburban Propane Partners

7.7

7.7

Pre-Paid Legal Services

9.4

7.6

Knoll

7.4

6.5

Advance America (NYSE: AEA)

9.3

6.0

ProAssurance

9.5

6.0

American Physicians Capital

8.1

5.2

EMCOR Group (NYSE: EME)

8.7

4.9 Continued...