Open GL specs  are maintained by the Khronos group.

There’s a couple of tutorials out there that stand out a little

  • OpenGL-ES tutorials at Zeus-CMD.com – A collection of 25 well written OpenGL-ES tutorials. While the sources won’t run on the iPhone (seems to target Windows Mobile), the tutorials expose very little platform specific code and can easily be uselkd in conjunction with basic OpenGLES examples.
  • Lessons From Molecules - This article from Sunset Lake Software contains many useful insights into OpenGL ES for iPhone.

Also check ManiacDev’s 18 OpenGL ES Resources.