Warning: This page is cool.
Nothings.org -- Sean Barrett's personal homepage. Excellent stuff. To be short sighted, checkout the 'free C source code' section on the index.
Fabian Giesen's Wordpress blog -- This guy is probably my favorite programmer.
Agner's Software Optimization Resources -- One of the greatest pages on software optimization.
OS Dev.org Wiki -- pretty cool Wiki & forums about Operating System development.
Unreal Features - archived document from Epic Games.