Came across this compilation of free books at the Assayer.
O'Reilly also has an openbook project where you can find a good no. of free programming books.
My favorites include:
- How to Design Programs: An Introduction to Programming and Computing
- Linux Shell Scripting Tutorial: A Beginner's handbook
- Embedding Perl in HTML with Mason
- Thinking in Java
- Thinking in Patterns with Java
- The Art of Unix Programming
- Philip and Alex's Guide to Web Publishing
- WEB STYLE GUIDE
- CGI Programming on the World Wide Web
- Open Sources: Voices from the Open Source Revolution
- The Cathedral and the Bazaar
Well, these are the books that I have read beginning-to-end or have browsed on need basis and have found them to be useful/thought provoking. I am sure there are others in the list that are better or eaually good.