These are my recommendations after alot of research and reading:
Prolimatech Megahalems - Platinum Micro $59.99
Cooler Master Hyper 212+ - Newegg $37.50
Scythe Mugen 2 Rev B. / SCMG-2100 - Newegg $40
Also check out my thread on the same topic: Which i7 Heatsink?
Has alot of good links to reviews of the top CPU heatsinks out there.