Depending on the socket used, you can go with:
1) Cooler Master Vortex Plus for $25.99
newegg linky
or if you want it cheaper:
2) ZALMAN CNPS7000V(AL)-1-PWM for $11.71
newegg linky
They're both decent enough coolers for stock speeds. There might be others that fall inbetween pricing wise/performance wise, but those are the 2 that come in mind off the top of my head.