There are (at least) 3 good questions on "free books" available on the web:
- List of freely available programming books (asked Oct 11 '08, 119 answers)
- What are some good free programming books? (asked Dec 24 '08, 98 answers)
- Language Books/Tutorials for popular languages (asked Aug 22 '08, 50 answers)
Every time I come across a good book and I'd like to add it, but I'm not sure to which thread..