image effects tutorials / Advanced Shaders

Hi,

I think e.g. the Twirleffect of Unity Pro looks just great and I can imagine a lot of different fields of application were I would love to use such or custimozed image effects (imageeffects).

I know some basics about Shaderlab... but I have only little knowledge about OpenGL, Cg, GLSL or whatever I need to write such effects.
I had a look at the Unity Docs and found nearly nothing about this topic... :cry:

I own an OpenGL book but don't know where to start... not even which chapter. :?

So... where can I find Documentation, Tutorials, Introduction, Tips Tricks, Hints etc. about image effects in connection with ShaderLab ?
Where should I start and what should I ignore... since some things seem to be included by default.

Also I am interested in Advanced Shader programming.
Where can I find good resources about this topic ?

 

The Unity manual does include a pretty good section on shaders:

http://unity3d.com/Documentation/Manual/Shaders.html

But I can't imagine diving into that stuff without a comfortable knowledge of OpenGL. I'd get familiar with that, first:

http://www.opengl.org/