Every quarter, fund managers have to disclose what they've bought and sold. Their latest moves can shine a bright light on smart stock picks.

Today let's look at investing giant Carl Icahn, who has made billions, partly by taking large positions in companies and pushing for change in them. These companies have included Texaco, RJR Nabisco, and Imclone. He's also drawn to companies in or near bankruptcy, wanting to make them more valuable in order to sell them at a higher price.

Icahn's stock portfolio totaled $11.7 billion in value as of Dec. 31, 2011, with just 11 holdings. Its top three holdings, Icahn Enterprises, El Paso (NYSE: EP), and Motorola Solutions, make up a big 56% of the overall portfolio's value.

Interesting developments
So what does Icahn's latest quarterly 13F filing tell us? Here are a few interesting details.

New to the portfolio is CVR Energy (NYSE: CVI), a petroleum refiner that focuses on transportation fuels and also deals in some fertilizers. The stock took a big hit late last year when it looked like a certain oversupply in oil that had been keeping prices low and benefiting refiners would be reversed, threatening CVR's profits.

Given this new purchase and the fact that nearly 17% of Icahn Capital's money is in El Paso, another energy company, it's clear that Icahn sees some value in the industry. El Paso is in a bit of flux, as Kinder Morgan plans to buy it, and its exploration and production business might be sold off.

Icahn Capital more than doubled its stake in WebMD Health (Nasdaq: WBMD), a company that struggled with net losses and the departure of a CEO. Icahn is campaigning for WebMD to buy back some of its shares, as he sees them as very undervalued. The company seems to concur, deciding not to sell itself, as it wasn't being offered adequate sums.

Icahn Capital's stake in Motorola Mobility (NYSE: MMI) was pared back by 10%. The company is being bought out by Google -- largely for its valuable patents. It's also looking into building mobile phones with Intel architecture, which could be a win-win arrangement for the two companies, if consumers are open to the idea of Google hardware.

Finally, Icahn sold out of Vector Group (NYSE: VGR) and Clorox completely. Clorox rejected an $11 billion takeover bid by Icahn and is reportedly interested in making some acquisitions in the health-care arena. Tobacco concern Vector, while attractive to some due to its near-9% dividend yield, also has some worried about its long-term prospects, as the ranks of smokers are no longer growing reliably, and increased taxes and regulations are making profits harder to come by.

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

For instance, Icahn's energy picks jibe well with what our Fool analysts believe about the future of the energy industry. We've recently called out three companies that will benefit the most from $100 oil -- check out our special free report to see which.