The latest 13F season is commencing, when many money managers issue required reports on their holdings. It can be worthwhile to pay attention, as you might get an investment idea or two by seeing what some major investors have been buying and selling.

For example, consider Appaloosa Management, founded by investing giant David Tepper, and known for investing in the debt of companies in distress. Tepper's investing history includes debt and stock in companies such as Enron and Worldcom. He made billions on bank stocks in 2009, after they had imploded and before they recovered. More recently, he invested in many housing-related companies. In a letter to shareholders last year, Tepper noted that, if one had invested $1 million in his hedge fund in 1993, it would have grown to $149 million during the past 20 years. Investing in the S&P 500 instead would have left you with $5.3 million. Tepper's performance reflects an average annual net gain of 28%. Wow.

Appaloosa Management's latest 13F report shows that it reduced its positions in Chimera Investment Corporation (NYSE:CIM), Fusion-io, (UNKNOWN:FIO.DL), and SanDisk Corporation (UNKNOWN:SNDK.DL).

Chimera Investment is a mortgage REIT (mREIT) that profits from mortgage-backed investments, and yields a whopping 11.3%. Bears worry about its vulnerability to interest-rate swings, but Chimera got a boost recently when new Fed chair Janet Yellen said that she aims to keep rates low for the time being. Chimera's stock has been in penny-stock territory lately, and it may not be able to maintain its listing on the New York Stock Exchange. It has also been the subject of some accounting-related head-scratching. A recovering housing market can help Chimera's prospects, but it might still not be the best bet in that arena.

Fusion-io is focused on technologies such as flash memory and solid-state drives, and has been turning itself around following lowered expectations and the departure of some key executives. Its second quarter featured estimate-topping revenue and earnings that sent shares up, but both numbers have been shrinking. Management noted: "As cloud computing and web services continue to grow, our customers invest in flash in tandem with their own customer growth. These investments are often substantial, but as we've said in the past can be non-linear in nature." With its industry consolidating, some see Fusion-io as an acquisition target .

Flash-memory specialist SanDisk reported a strong fourth quarter, with revenue up 12% over year-ago levels, and non-GAAP earnings surging more than 50% thanks to a profit-margin expansion. Its solid-state drive (SSD) business is growing briskly, and has benefited from the spread of mobile technology. Bulls like its prospects in China, as it supplies mid-market smartphones, among other things. Bears worry about pricing pressures and whether SanDisk can keep costs under control. The company initiated a dividend last year, and it recently yielded 1.2%.