Some excellent political sites from Fred Lapides:
The Cold War International Project contains a very deep selection of key documents related to communism. Best of all, this project organizes the documents by subject, location, and other filtration methods.
Next, in George Washington University's National Security Archive, great source documents are available on the Pentagon Papers and Nixon's paranoia. Streaming audio of phone conversations, US Supreme Court opinions, and memoirs are all available.
Finally, here's a great site on Charles Bukowski. Not very political, but you can read his FBI file. (Thanks to Natalia for the photo).