Institutional investors are required to disclose their significant holdings to the Securities and Exchange Commission through a Form 13F filing. One investor that filed today was billionaire activist investor Carl Icahn and his fund Icahn Capital LP’s activity for the period ended December 31, 2007. Although the investor has experienced issues with some of his holdings, he is still a large player in the market that is definitely worth watching given his spectacular annualized returns. So, without further adu, here are his major holdings:

1. Anadarko Petroleum (NYSE: APC) $970.6 million
2. BEA Systems (NDAQ: BEAS) $654.176 million
3. Biogen Idec (NDAQ: BIIB) $469.973 million
4. CSX Corp.(NYSE: CSX) $128.422 million
5. Lear Corp. (NYSE: LEA) $265.424 million
6. Macy’s (NYSE: M) $133.61 million
7. Motorola Inc. (NYSE: MOT) $969.881 million
8. J.C. Penney (NYSE: JCP) $183.274 million
9. Regeneron Pharma (NDAQ: REGN) $60.586 million
10. Temple Inland (NYSE: TIN) $71.9 million
11. Time Warner Cable (NYSE: TWC) $130 million
12. Time Warner Inc. (NYSE: TWX) $213.526 million
13. Unum Group (NYSE: UNM) $95.65 million
14. Williams Cos. Inc. (NYSE: WMB) $173.2 million

Investors can track Carl Icahn’s portfolio via the Schedule 13F filings; activist communications through Schedule 13D filings; and buying and selling through Form 4 filings. These are all filings that can be tracked through SECFilings.com and are definitely worth watching closely!