"But, somewhere along the line, a variety of hard drives were tossed into a canal leading to Chicagoâs Wilmette Harbor. These were recovered and found to be storing alpha terms and alpha data." Note to myself: Buy giant magnet, water doesn't work....
+1 Water works (depending on the type of drive) if the drives are left in the river long enough, but do you want to take the risk? Burning the drive, literally is the only sure way to destroy the data. Oh, and a magnet, no matter how big does not work. And if drilling holes in it is your method of choice be sure to make Swiss cheese out of it and know that the data in between the holes is still recoverable. Better to be safe and melt the damn thing.
first use a utility to wipe drive with all 0's, all 1's and then random then use something like this <iframe width="560" height="315" src="http://www.youtube.com/embed/S_BgtldCwqw" frameborder="0" allowfullscreen></iframe> then incinerate the remains if you are really paranoid
How about a microwave oven? I use one for CDs & DVDs, I've often wondered if it would fragment/destroy the face of a HDD as well. If you haven't tried it, it only takes a few seconds and it is quite a "light show." There's always a wood chipper.