- The Art of Computer Game Design by Chris Crawford (1984) [PDF]
- Balance of Power by Chris Crawford (1986) [TXT]
- The Complete Wargames Handbook (Second Edition) by James F. Dunnigan (1997) [HTML]
- GPU Gems (2004), GPU Gems 2 (2005), GPU Gems 3 (2007) [HTML]
- The Cg Tutorial by Randima Fernando and Mark J. Kilgard (2003) [HTML]
- Pangea Software’s Ultimate Game Programming Guide for Mac OS X by Brian Greenstone (2004) [PDF]
- Invent Your Own Computer Games with Python by Al Sweigart (2010) [PDF]
- ShaderX2: Shader Programming Tips and Tricks with DirectX 9.0 by Wolfgang Engel (2003) [PDF]
- ShaderX2: Introductions and Tutorials with DirectX 9.0 by Wolfgang Engel (2003) [PDF]
- Direct3D ShaderX: Vertex and Pixel Shader Tips and Tricks by Wolfgang Engel (2002) [PDF]
- Michael Abrash’s Graphics Programming Black Book by Michael Abrash (1997) [PDF]
- Action Arcade Adventure Set by Diana Gruber (1994) [HTML]
- Designing Arcade Computer Game Graphics by Ari Feldman (2000) [PDF]
Culture and Studies
- ETC Press: ETC Press have been published plain text version of their books for free.
- Well Played 1.0 by Drew Davidson et al (2009)
- Beyond Fun: Serious Games and Media by Drew Davidson et al (2008)
- Ludoliteracy: Defining, Understanding, and Supporting Games Education by José P. Zagal (2010)
- Toward a Ludic Architecture: The Space of Play and Games by Steffen P. Walz (2010)
- Cross-Media Communications by Drew Davidson et al (2010)
- Trigger Happy by Steven Poole (2001) [PDF]
- Gamer Theory 2.0 by McKenzie Wark (2007) [HTML]
- Playing to Win by David Sirlin (2006) [HTML]
- PSX: The Guide to the Sony Playstation By Kevin Bryan (2005) [PDF]
The Real-Time Rendering website has a good list of free books. They’re mostly about writing shaders, including books from the GPU Gems and ShaderX series.
I have never read it myself, but I keep seeing it mentioned.
I believe it is mostly text games, but near the end it covers pygame.