
Here's a crafty solution to noisy hard disks: suspend it with elastic! Jason @ HACKS provides us with this visual tip.
As the pictures show, the drive is essentially suspended on the stretched elastic. The resilience of the elastic stops all vibrations from passing from the drive to the case -- or vice versa, for that matter. Keep in mind that you'll loose some of the conductive cooling that you get when the drive is mounted to the case, so it'd be smart to do this in cases where there is decent airflow or find a way to attach some sort of heatsink to the bungeed drive.
http://blog.makezine.com/archive/2008/04/nix_noisey_hard_drives_wi.html