I've added three new projects to my iOS OpenGL ES repository on GitHub. They are fairly simple examples of how to use GLKit and GLKBaseEffect. You can find them in the GLKit Stuff directory.
They're kind of rough, but they should be helpful to you if you're just getting started with GLKit and trying to figure out how to use it.
Thanks to Julián Oliver for tweeting the solution to a problem I was having getting textures to work with GLKBaseEffect.