[golem14]

For quickly destroying hard drives, drive big nails through the entire case in several places. Restoration is at least very manual and annoying, in many cases not worth the effort.

If you need more security, building a simple furnace isn't too hard:

http://eecue.com/c/driveslag

[mirimir]

You don't need to go that fancy. Just use a small steel drum, with holes punched around the bottom, sitting on bricks. Burn dry hardwood, plus occasional chunks of paraffin. Everything burns off, except for the steel.