o_O rubber band idea might work... I don't have any shelves though. The cabinent has 3 levels - bottom, w/ keyboard tray and (removed) writing tray, monitor area (where tower/monitor/speakers/external HD is), and an upper level where I toss all my random stuff. I might find a way to pull it off (hooks attached to bottom of top level?). Dunno yet.
It was originally on my carpet floor, but I don't have a patch of carpet available. We had carpet samples, but my mom threw them out recently (I'm looking around the house with my dad for any unused carpet, we have 2 large 3'x3' sections, but that's a bit too large for 2"x6"). That's a good idea though, and one that I didn't think of (I moved it off of carpet, but didn't think to use carpet again).
We don't have any gelatin-like stuff, though, so that's out.
Things to try: Carpet section, hooks+rubber bands.