Shaderific is a great iOS application for OpenGL ES shader learning. The app provides the source code for the vertex and fragment shaders for 18 built-in demo shaders, and it allows the creation of new ones. Many 3D objects (including the required teapot) are available, and material and lighting can also be set. There is a free version that lets us try it out, but the changes are not kept once the app is closed.
