Well I use a Cooler Master V8, but really I'd say any big cooler, (lots of heatpipes, metal fins), will do the job as long as it has a nice big 120mm or bigger fan on it. Keep that fan below 1000 RPM during idle, and it is supppppper quiet.
Look at frosty's list if you want more info on CPU coolers though, there is always sound info there.http://www.frostytech.com/top5heatsinks.cfm
Look at this cooler, it's under AMD low noise top coolers, in first place.http://www.frostytech.com/articleview.cfm?articleID=2258
Looks pretty good, not the coolest, but definetely very silent even under full load. Temps for this are still very acceptable.
just make sure your case is big enough.
If you really want perfectly quiet you could consider water cooling, I hear zalman makes a passive reservior which works well, just empties your wallet.