I've been given the task today to destroy a bunch of CD's, floppys and data off of all my backups. I'm not sure of the proper way to do any of this.
How do you ensure that you've put all information on a CD/DVD permanently out of anyone else's reach? I've tried scratching the surface of one I'm throwing out, but have heard that isn't enough; data can still be retrieved.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic