This page links useful resources for learning OpenGL ES on iPhone.

Online

Open GL specs  are maintained by the Khronos group.

• OpenGL-ES 1.1 API Specification (PDF)
• OpenGL-ES 1.1 API reference (online browsing)
• Apple’s OpenGL ES programming guide for iOS - while this won’t teach you OpenGL, it will help you reason optimization issues and understand device limitations.
• iPhone 3D Programming – Currently (May 2012) you can access this book online. It looks AWESOME – maybe one of the rare books that will teach you GPU programming from the ground up, do it well, introduce you to advanced topics and provide good sample code.

There are 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 useful insights into OpenGL ES for iPhone.

For more resources, check ManiacDev’s 18 OpenGL ES Resources.

On the blog

I have written a few tutorials. These tutorials target OpenGL ES 1.x

• Open GL ES 1.x / 2.x quick facts
• How does the GL work?
• Skipping started
• Setting up an isometric view (maybe check this linkas well)
• Lighting quick reference