Hard Disk Temperature

hddtemp is a small utility that gives you the temperature of your hard drive by reading S.M.A.R.T. informations (for drives that support this feature). 

Note: only recent hard drives have a temperature sensor.

The temperature information seems to be vendor specific (i.e. not standardized). So hddtemp comes with a file (hddtemp.db) that contains informations about drives that were reported to work with hddtemp.