e-book torrents.

It's time to exchange some knowledge. I'll start:
http://www.btmon.com/Video/Unsorted/1136ComputerEbooks.torrent.html

Math, physics, science, software, and philosophy e-books are fine too.

reddit finally comes in useful
http://www.reddit.com/r/csbooks/
http://www.reddit.com/r/compsci/comments/911h7/150_computer_science_books_for_free/
http://www.reddit.com/r/programming/comments/8jt9w/300_free_programming_books/