Slashdot posted a thread titled, "Secure Hard Drive Deletion Appliance?" It contains some helpful answers for deleting and removing data off hard drives.
DBAN, Darik's Boot and Nuke CD-ROM, was mentioned and it is my tool of choice for wiping hard drives at the office. Other interesting tool and notes include:
- Ultimate Boot CD, http://www.ultimatebootcd.com
- BCWipe [jetico.com] to declassify secret hard drives
- http://www.driveduplicators.com/124.html, Its primarily a hard drive duplicator but it also has DoD 5220.22-M level wipe
- VIDEO - Destroying Drives with Acid and Thermite
- Discussed to death by experts, http://www.securityfocus.com