At The Motley Fool, we understand that it often pays to zig when Wall Street zags, but that doesn't mean that we don't pay attention to what leading fund managers are buying and selling. And hedge funds that aren't always in lockstep with the broader market, can be a particularly valuable source of insight.

Every quarter, fund managers overseeing more than $100 million must disclose their quarter-end holdings publicly by filing Securities and Exchange Commission Form 13-F. The form lists all U.S.-traded securities the manager held at the end of the quarter. Although the form doesn't disclose the manager's short positions or the manager's intraquarter trades, it can shine a bright light on his or her "long" stock bets. To help us make use of 13-F data, we turned to Motley Fool partner AlphaClone, a research and investment-management firm that tracks hedge fund public disclosures and develops investment strategies based on them.

Q2 2011 update
Value investor David Einhorn founded Greenlight Capital, where his investing success -- and his advocacy of financial transparency and accountability -- have attracted many fans. Although Einhorn isn't afraid to short stocks, he prefers to go long, and looks for situations where he feels a stock is mispriced.

Why should you look at Greenlight Capital's moves? According to AlphaClone's back-test simulation, anyone who invested in Greenlight's 10 largest long positions at the time they were disclosed publicly each quarter would have returned 210% since 2000, versus ... uh, 4% for the S&P 500 (including dividends) as of Aug. 31.

The total market value of Greenlight Capital's disclosed equity holdings as of June 30, 2011 -- the latest quarter for which data is available -- was $4.6 billion across just 35 holdings. The fund company's 10 largest positions and associated changes in number of shares held as of June 30, 2011 were:

Pfizer (NYSE: PFE) -- reduced 6%.
Microsoft (Nasdaq: MSFT) -- increased 63.4%.
Apple (Nasdaq: AAPL) -- increased 28.7%.
Sprint (NYSE: S) -- unchanged.
Carefusion -- reduced 5%.
The Travelers (NYSE: TRV) -- unchanged.
Ensco plc (NYSE: ESV) -- reduced 4.2%.
Best Buy (NYSE: BBY) -- increased 14.8%.
Becton Dickinson (NYSE: BDX) -- unchanged.
Market Vectors Gold Miners -- unchanged.

During the quarter, Greenlight Capital also increased its position in Seagate Technology (Nasdaq: STX) and Ingram Micro, among others. Among the stocks that it reduced its exposure to were BP (NYSE: BP) and Employers Holdings. Also, Greenlight sold out of Xerox (NYSE: XRX) and Yahoo! entirely.

Einhorn's decision to buy more Microsoft shares may have owed partly to the stock's decline during the period. That slump made the company even more of a bargain to those attracted by its massive cash coffers, and intrigued by its promising new mobile operating system, Mango. The Xerox sale may stem from a lack of confidence in the company's ability to expand overseas and shift from a business-equipment company to a business-services one.

Selected Q2 2011 commentary
Greenlight Capital is fairly well-diversified, with about 27% of its assets in the technology sector. It has boosted its services holdings considerably, at the expense of cutting back on financials. When it comes to the financial sector, Einhorn isn't alone -- much of the market has also lost faith there, thanks to shrinking loan books, scandals, and other woes.

Here's where Greenlight Capital is currently winning, losing, and making new bets:

Recent winner
Best Buy was a winner for Greenlight in the quarter, rising about 10%. Among other things, the company reported strong mobile phone sales during the quarter, and it has big stock buyback plans. The company has created many skeptics, though, as evidenced by its share drop since June and its two-star rating (out of five stars) at Motley Fool CAPS.

Recent loser
Fifth Street Finance (NYSE: FSC) didn't do so well for Greenlight, dropping more than 11% in the quarter. Einhorn hung on to his shares, though, and insiders were buying more. The stock has fallen sharply and recently sported a dividend yield near 13%. Fifth Street Financial lends money to small and medium-sized companies, and also makes some equity investments. The company has a four-star rating in Motley Fool CAPS.

New bets
The largest new addition to Greenlight is Huntington Ingalls Industries, a maker of both nuclear and non-nuclear ships for the military. Spun off from Northrop Grumman, the company doesn't look like a slam-dunk, as it carries considerable debt, is burning a lot of cash, and faces the loss of some business. The company has a three-star rating in Motley Fool CAPS.

During the quarter, the company also started new positions in Marathon Oil and Aeropostale.

We should never blindly copy any investor's moves, no matter how talented the investor. But it can be useful to keep an eye on what smart folks are doing. 13-F forms can be great places to find intriguing candidates for our portfolios.

Have any thoughts on this fund company or its holdings? Leave a comment below!

Longtime Fool contributor Selena Maranjian owns shares of Microsoft and Apple, but she holds no other position in any company mentioned. Click here to see her holdings and a short bio. The Motley Fool owns shares of Ensco, Best Buy, Microsoft, and Apple. Motley Fool newsletter services have recommended buying shares of Becton, Pfizer, Apple, Microsoft, and Best Buy, as well as creating bull call spread positions in Microsoft and Apple. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.