For drives that are still operational, we usually do a multi-overwrite. For drives that are not operational, we usually take them apart, rub the platters with the drive magnet, and microwave them for a while in a spare microwave.

After wiping one way or another, we hire a company to shred the discs - drive and all. For that matter, we've seen some shredders large enough to drop entire servers into (but they make larger pieces). http://www.semshred.com/content291.html has more information.

We've also hired a special shredder truck from Tennessee that could shred metal. Neighbors came out to see if an airplane had landed in the parking lot because the thing was so loud. The particle size was larger than what you see in this photo, but these were from our stack of low-sensitivity drives that had accumulated.

I've heard stories of military drives being sanded down and the particles mixed with concrete, but I have not personally witnessed that process.

RE: Lazyweb: Hard Drive Degaussing