DevMaster.net: Game and graphics programming using OpenGL.
GameDev.Net: Forum dedicated to OpenGL game programming.
GLProgramming: Focuses on OpenGL programming for beginners.
Hybrid OpenGL ES Forum: Forum for Hybrid's OpenGL ES implementation (Gerbera).
iDevGames: The Macintosh OpenGL community forum.
Khronos Group OpenGL ES Forum: For discussion on OpenGL ES development.