http://www.webmastersbydesign.com/2008/06/19/the-best-developer-cheat-sheets-around/

Take a look this cheat sheet from the guys at webmasterdesign.com There is over 40 different cheat sheets to take a look at. Anything from HTML to Ruby to MySQL. Ive also come across the FreeTechBooks.com website in their categories section which has 600+ free online programming books. It lists computer science, engineering and programming books, textbooks and lecture notes all free and completely legal.