CG Talk: Big computer graphics community
CG Cars: All about virtual cars
Cartoon Brew: Animation blog
3d-WorXX: German CG community
blender.org: official Blender webpage
Blenderartists: best Blender userforum
Blendernation: really good Blender news site
3Delight: Renderman compliant renderer, one license is free
Aqsis: Renderman compliant renderer, no support for ray tracing
Freestyle: Non photorealistic renderer
Kerkythea: Renderer that supports different GI-methods
Luxrender: Artist-friendly GPL port of PBRT
PBRT: The ray tracer described in the highly recommended book Physically Based Rendering
Pixie: Renderman compliant renderer that supports even ray tracing and photon mapping
Sunflow: open source JAVA renderer
WinOSi: Renderer with the all-known renderer comparison scene
Yafray: Old GI renderer, but rewritten as Yaf(a)ray which is capable of making really nice images again