Free Programming Books

There was thread on Stackoverflow which contribute the list of free programming books. The Original Source for these free books as below:
 List of freely available programming books
Further I found a nice maintained list on GitHub – Free programming books and subset of the list is here:

Parallel Programming
Partial Evaluation
Professional Development
Programming Paradigms
Regular Expressions
Reverse Engineering
Security
Software Architecture
Standards
Theoretical Computer Science
Web Performance