http://homepage.mac.com/holtmann/eidac/software/page5/page5.html
Allows you to control the speed of your fans.
My macbook pro would get insanely hot, to the point it would actually burn my legs.
Apple has fan speed set 2000rpms for quite operation but I tuned mine up to 4500rpms and has dropped my temperature down from 140* to 110*