For nearly three years, from when I wanted to sell shaders on my website, I never really wrote usefull shaders for my webshop, so I didn´t sell much, but it makes my freelancing legal and didn´t do me any harm yet wink.

Lite-C Tut. 1 Lite-C Tut. 2 Lite-C Tut. 3 (en)
Shader Tutorial (ger)

http://www.slindev.com