GLSL coding question

Greetings. I’m trying to sink my teeths on the shading language and I’m clawing my way out of some holes.
I know I have to first learn the GLSL and I do understand the very basics, but it’s not easy to study it with bge.

So far I have managed to change the color. But the documentation for blender game engine and glsl is not all that clear to me. So this far I have only managed to get a shadeless colored objects.

Where could I find a very simple sample glsl shaders done for bge or links to tutorials showing how shaders work with game engine?