I use the Hyper TX3, most people use the Cooler Master 212 EVO. It's pretty much the same thing only bigger and is one of the best you can get without spending a ton of money.
I agree ...just installed one and am very pleased with the results for a $20+ investment (tax/ship) -- inside room temp in my den is about 80F (Phoenix, AZ), and it keeps my Intel i5-2550 at 39-44C at 0-10 load, and no more than 57C at loads up to 35-50.
This compared to 49-55C at 0-10L, and 65-80+C (leading to shutdown) at 35-50L on the standard Intel heatsink. Might have picked up 5C by just cleaning sink/CPU and applying Arctic SIlver, but that plus the Hyper TX3 is way better for very small $$ investment. Just be sure its compatible with your chip/motherbard setup.