Game Resources
Game textures, programming sites, open source games.
This seems to be a kind of open community of game makers that people can join by signing a contract. They then will allow you to use all their resources like textures, sounds.
http://gamebeavers.org
Quake was a big hit for the mod and game deve community and there are many resource sites relating to it. This seems to be a good one.
http://www.planetquake.com/
Free 3D models in several formats each, but not open source or anything, you probably cannot use them commercially.
http://www.amazing3d.com/free/free.shtml
This seems to have some free models for games.
http://www.psionic3d.co.uk/
An open source free game engine with a focus on quality rendering.
http://www.panardvision.com/v3