Silencing and Cooling Systems for Hard Disk Drives
 

Today we are going to talk about six solutions for cooling 3.5-inch hard disk drives. We will check the cooling efficiency and acoustic performance of products from GlacialTech, Scythe, Tuniq, Xilence and A.C.Ryan.

http://www.xbitlabs.com/articles/coo...r-roundup.html

the Quiet Drive from 2006 takes the cake :)
http://www.madshrimps.be/?action=getarticle&articID=517

If we can believe google, then there's no use in buying these things to cool down your hdd as they state that a hdd will survive longer at 55°c (which is the max. temperature most manufacturers seem to specify for desktop drives).
The only reason to buy these is to silence your disk (like the quiet drive does ;) ).