I was going to use these to blow air through the cowling of 4 Sapphire 5850 Extremes, but that seems unlikely to happen now.
They're 24V fans, but run fine on 12V with lower CFM. These have great static pressure, so they work well forcing air into constricted spaces like heatsinks.
4xComair Rotron BD24A3 (2BTC)
http://search.digikey.com/scripts/DkSearch/dksus.dll?WT.z_header=search_go&lang=en&site=ca&keywords=bd24a3&x=0&y=0
1xComair Rotron SPD24B1 (4BTC)
http://search.digikey.com/ca/en/products/032183/CR249-ND/166918
The big one weighs 2lbs, but will move an insane amount of air for its size.
Paypal or BTC, + shipping
