I'm always looking for a good deal, whether that means buying an extra box of Golden Grahams when they're on sale, or pouncing on undervalued stocks. The idea that anybody would sell a stock for less than its worth may seem silly, but legendary value investor Ben Graham (no relation to the cereal) tells us, by way of allegory, how we can look out for these situations.

In The Intelligent Investor, Graham introduces readers to a wacky guy named Mr. Market. Mr. Market's game is to pay you house calls on a daily basis, offering to sell you interests in businesses he owns, or to buy from you interests in businesses you own. Sometimes, Mr. Market will show up at your door very excited, offering you premium prices for your holdings. At other times, he'll be inconsolably depressed about the future, offering to sell you what he has for as low as pennies on the dollar.

To find some of the stocks that Mr. Market is currently depressed about, I've turned once again to The Motley Fool's CAPS investor community. Each of the companies below had been given a five-star rating (the highest) by our community of investors just 30 days ago:

Stock

30-day return

One-year return

Current CAPS rating

Northgate Minerals (AMEX:NXG)

(38.5%)

(48.2%)

****

Healthways (NASDAQ:HWAY)

(30.4%)

(59.8%)

****

A-Power Energy Generation Systems (NASDAQ:APWR)

(26.1%)

155.6%

****

NYSE Euronext (NYSE:NYX)

(18.9%)

(47.3%)

*****

POSCO

(15.7%)

(25.1%)

*****

Manitowoc (NYSE:MTW)

(14.9%)

(35%)

*****

ChinaMobile (NYSE:CHL)

(13.1%)

(9%)

*****

Data from Motley Fool CAPS as of Aug. 26.

As the table shows, these stocks are all still very well-regarded by the CAPS community, despite their underperformance over the past month. While these are not formal recommendations, they could be a great place to kick off some further research. I'll even get you started with some thoughts on Rule Breakers pick NYSE Euronext.

Why so blue?
There are both short-term and long-term storm clouds gathering for the NYSE. On the near horizon, investors are worried about trading volume, not only on the NYSE, but also on competitors like Nasdaq OMX Group (NASDAQ:NDAQ). Traders simply aren't passing as many shares back and forth lately, and since this is how the stock exchanges make a lot of their dough, it's not a good sign for results yet to come.

At the same time, the down market has new equity issuers about as excited to make their IPO debut as my dog is to get in the bathtub (namely, not at all). And with share prices down all over the market, the only companies issuing new shares are those that have no other choice. Neither of these facts is good news for NYSE.

Meanwhile, the bigger picture has some smudges of its own. The emergence of electronic exchanges has been a thorn in NYSE's side since it first heard the acronym "NASDAQ." Today, though, electronic exchanges seem to be popping up left and right, and some are starting to become more than a small nuisance. Kansas City-based BATS, for example, now handles more than 12% of total U.S. trading volume, and it just recently won approval from the SEC to become an exchange. In short, it seems like "NYSE" stands for "Now You Should be (at least a little) Edgy."

What the bulls say
To the bulls, NYSE is the Coca-Cola of the stock market exchange picture. Sure, Nasdaq may be the Pepsi to NYSE's Coke, but that makes BATS what? Ginger ale? Dr. Pepper? We all know someone that drinks ginger ale, but let's be serious, it's never going to unseat Coke.

On CAPS, more than 2,100 members that think NYSE's size, presence, and brand will help it outperform the broader market, while a paltry 75 that think it will lag. CAPS All-Star DemonBzer was bold enough to say "[NYSE] is like betting on capitalism" when he rated the stock an outperformer last year. More recently, FGunawan saw the stock's sell-off as a great opportunity to hop on board:

The recent sell-off on [NYSE] provided an unparalleled opportunity to own a piece of the stock exchange we all use. With an estimated forward P/E of 13, this is an easy call to make.

So do you think the recent drop has created a good buying opportunity? Or is there more downside ahead? Let the community know what you think -- head over to CAPS and share your thoughts with the other 115,000-plus players currently part of the community. Even if you'd prefer to pass on NYSE, you can check out a couple of the other stocks listed above or any of the 5,500 stocks that are rated on CAPS.

More CAPS Foolishness:

POSCO is an Income Investor pick. Nasdaq and Coca-Cola are Inside Value selections. NYSE Euronext is a Rule Breakers pick. Healthways is a Stock Advisor recommendation. Try any of our Foolish newsletters services free for 30 days.

Fool contributor Matt Koppenheffer does not own shares of any of the companies mentioned. You can check out what Matt likes in CAPS by visiting his CAPS portfolio. The Fool's disclosure policy knows how to drop a stock like it's hot, but only when the company is truly cold.