like CHiMPBizKiT, i got a chinsy 3-50mm-fan blower (sucker). It actually works sorta well. Less effective in some setups than others, since
1) the 3 fans dont provide much flow to begin with
2) for heavy OC'ing, with a lot of fans, you should have high(er) case pressure, which reduces the effectivness of these 50mm fans when trying to blow into the case
3) there isnt much ducting of the existing airflow onto the drive. I have a big case, lots of room, I need to put in a shroud to make sure all my flow is going over the drive and not into the drive slots above/below. this is a problem with my setup, and not the cooler per se.
ill never run a 7200rpm without a cooler of some sort. next time ill probably go with either the 'Ultimate' Harddrive Cooler by Vantec, or GlobalWin I-Storm II
oh, and wrt/dust in the case...it never ever seems to collect on the drive itself, just on the fans (needs blown out every 4mos or so).
YMWV.