Once you have them you wonder how you ever survived without!

http://www.inagoni.com/news.php

http://www.des-web.net/shoestring_graphics.html

http://www.digitalcarversguild.com/

http://www.sparrowhawke3d.com/
The Sparrowhawke ones are free

I would put the DCG Shader Ops and Shaders Plus amongs the first to get perhaps.

Brian
 

bwtr