600+ Free Online CS and Programming Books
FreeTechBooks.com is a website dedicated to programming books, textbooks, and notes. The content is 100% free and 100% legal. There are hundreds of books spread out among seven main categories with many subcategories within each main category. The seven main categories are Computer Science Books, Mathematics Books, Supporting Fields Books, Operating System Books, Programming/Scripting Books, Miscellaneous Books, and General.
You can find the books you are interested in by using the main and subcategories mentioned above, by looking at the most popular books listed on the left hand menu, or by using the search function to locate a book based on keyword(s), author(s), and/or other criteria. The site is updated regularly with news and comments as well as regular additions to the book collection, the most recent being the IT Security Cookbook, which was added on August 16, 2008.
Beyond the books, there is a community that you can register and be a part of. This allows you to post comments to the forum as well as be in contact with the other people that are interested in the same type of information you are. Registration is not necessary, but it is an option.
Be sure to check out the website and get all the free information you can. This is a great free and legal resource that allows us to "view, download and with a very few exceptions, print the books for your own private use at no charge. In fact, you are encouraged to tell others about the books" (FreeTechBooks.com).