Well, I recently got the Zalman 7000A-AlCu for $30, and I really like it. The only reason I preferred it over some of the less expensive solutions was that it can be used on pretty much any CPU platform. I hope to be able to re-use mine when I go to a 754 or 939 based system later this year.
Depending on your upgrade plans, it may be worth it to spend the extra money if you can re-use the heatsink on your next computer.
-D'oh!