smartmontools is a very informative tool!
smartctl -a /dev/sg2 will show lots of information from my harddrive
/dev/sg3 is the other drive.
for instance Current Drive Temperature reads 37 C
and 40 degrees C for the other.
And has been working for 34258 hours
hddtemp is a other useful too which as you probably figure out, show you harddrivetemperature: also an debian package ready to apt-get install.
hddtemp /dev/sg2 /dev/sg3
/dev/sg2: IBM-ESXSST373453LC FN: 37°C
/dev/sg3: IBM-ESXSST373453LC FN: 40°C