Speedfan is the only one I know of, but a fan controller is probably the easiest way to control fan speeds (of if you have an ASUS mobo, cool'n'quiet it good as well)
Hm. I have an MSI board, and it has cool and quiet. I think most boards that support OCing have cool and quiet which is a program that has cooling crap in it. Otherwise, a fan controller is pretty cool. I'll definitely have one in my Q6600 Build.