Graphics
AssistCG - http://www.assistcg.com/
Features free professional downloadable seamless textures 1024x1024px and higher, video transitions, video compositing, video effects, and educational materials.
CGTextures - http://www.cgtextures.com/
Features more than 50.000 high resolution textures, free for personal and commercial use.
Wetzel and Company, Inc. - http://www.wetzelandcompany.com/
Features photoshop backgrounds, stock photography, and textures for the photoshop beginner or pro.