SMART is a technology that hard drives use to perform self-checks. This can generally tell when a drive is "about to fail." You can get the SMART status of your hard disk from the command line with the following command:
% diskutil info disk0 | grep SMARTIf you only have one hard disk, it is generally disk0; if you have others, run:
% diskutil listto find their numbers. Someone with more time on their hands than I can probably roll this into a shell script that's run via a cron job, checking, say, once a day, which can alert users when the disk is about to fail. Since no one thinks of checking regularly, this info could be a real lifesaver.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20031122041138373