If you go through a lot of hard drives for projects,
here is a cool product. It's a sata drive docking station. You push in a bare 3.5" or 2.5" drive, hook up the station to your PC with a USB2 cable, and use the drive as though it were normally installed. It's at CircuitCity (mail orders only) and after a $10 rebate it's only $25!
Only downside I can see is that the drive is bare naked while in use. Also, how do you store such naked drives cheaply? Still, for $25...
I predict these will sell out quickly. There is a fancier version coming out with covers for the drive and extra USB ports, but for $25 how can one go wrong?
EDIT:
Oh, free shipping too.