Whenever I've trashed hard drives, which has been somewhat rare - I keep them on a shelf, I've used it as a lesson to my kids as to how they work (if I can get the case open in a reasonable time).

There is a bit of magic for them seeing the platters and the tiny little read/write heads on the arms - and telling them that all of the music, photos, school assignments, etc. actually exist as little magnetic deviations on the platters and the little arms are what put them there and read them off.

Then we take it out to the driveway and get the 2 lb sledge and I tell them to have fun beating the living daylights out of it! I tell them to make sure that each of the platters is bent all to pieces. I've done this with 2 of my 4 kids. They learn and then they have fun (hopefully the learning was fun also).