I use this one right now:
Data sheet:
http://store.yahoo.com/directron/volcano7.html
I have no complaints. It's quiet, variable, and moves a lot of air.
Edit: The data sheets show support up to 2000+, but that's all there was when this volcano came out. But I can say that it pushes more air than the fans that come from AMD in the retail box for the newer processors.