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The D programming language, designed as a successor to C++. Very intriguing, although the toolchain is a little immature right now.
Humus' site Featuring tons of 2D and 3D effects, among others.
opengl.org THE OpenGL center.
gamedev.net Well-known site about game development. Filled with interviews, tutorials, news etc.
Hugo elias' homepage Site with excellent material from the author of Terragen.
Pouet.net For your daily dose of demoscene.
Nectarine demoscene radio Demoscene webcast.
music-dsp source code archive Very useful link if you plan to code your own realtime sound stuff.
Catch22 Programming site with focus on Win32 WINAPI coding.