ZALMAN ZM-NB47J (http://www.zalman.co.kr/ENG/product/Product_Read.asp?Idx=131)
I bought this to replace a northbridge heatsink/fan on my sister's Asus A8N-E motherboard. The fan on the original cooler had become the single loudest fan on this thing. I found it very irritating and was concerned it was possibly on its last days.
Read a few reviews and decided on the ZALMAN ZM-NB47J and am very pleased with the results. Oh, the joy of no moving parts.
Installation was straight forward although I did have to remove the motherboard from the case to release the pins that held the old chipset cooler in place. The Zalman has a very adjustable mounting situation with a couple of sliding arms and pins. They do include a small tube of white paste, I did however use a silver colored paste. The only downside is the very tiny screws and nuts used for assembly, not a big deal. It's best to do a trial run and make sure everything is aligned to fit before applying paste.
I bought this at newegg for 3.99.
I've used the NB47J on a couple of boards, and its always performed well for me. Amazingly it works better than the stock heatsink with a whiny fan.