Language

• The C book
• The new C standard - an annotated reference

C+

• Thinking in C++
• C++ Annotations
• How to Think Like a Computer Scientist
• Software optimization resources by Agner Fog
• Effective STL by Scott Meyers
• More Effective C++ by Scott Meyers

  C

  • .NET Book Zero: What the C or C++ Programmer Needs to Know About C# and the .NET Framework
  • Illustrated C# 2008(Dead Link)
  • Data Structures and Algorithms with Object-Oriented Design Patterns in C#
  • Threading in C#

Common Lis

• Practical Common Lisp
• On Lisp

Haskel

• Real world Haskell
• Learn You a Haskell for Great Good!

Jav

• Thinking in Java
• How to Think Like a Computer Scientist
• Java Thin-Client Programming
• OSGi in Practice(CreativeCommons Attribution Non-commercial Share Alike License)

JavaScrip

• Eloquent JavaScript
• jQuery Fundamentals(starts with JS basics)

Lu

• Programming In Lua(for v5 but still largely relevant)

NoSQ

• CouchDB: The Definitive Guide

Objective-

• The Objective-C Programming Language

Per

Perl

• Beginning Perl
• Extreme Perl(license not specified - home page is saying "freely available")
• Embedding Perl in HTML with Mason(Open Publication License)
• Practical mod_perl(CreativeCommons Attribution Share-Alike License)
• Higher-Order Perl
• Learning Perl the Hard Way
• Perl & LWP
• Perl for the Web
• Web Client Programming with Perl
• Modern Perl 5(Work in progress)

Perl

• Perl 6(Work in progress)

PH

• Practical PHP Programming
• Zend Framework: Survive the Deep End

Prolo

• Building Expert Systems in Prolog
• Adventure in Prolog
• Prolog Programming A First Course
• Logic, Programming and Prolog (2ed)
• Introduction to Prolog for Mathematicians
• Learn Prolog Now!
• Natural Language Processing Techniques in Prolog

Pytho

• Dive Into Python
• Dive Into Python 3
• How to Think Like a Computer Scientist
• A Byte of Python
• Python for Fun
• Invent Your Own Computer Games With Python
• Thinking in Python

Rub...