Although somewhat more expensive than rubber feet, Auralex Acoustics also has a line of isolation products. I use the MoPads: http://www.auralex.com/sound_isolation_mopad/sound_isolation_mopad.asp for my center channel speaker that sits on top of my television. I noticed a difference immediately.

I think they were $25 for a pair of them (4 pieces total) and I split them with a friend and he uses them for his center channel as well.

[This message has been edited by kugumby (edited September 03, 2004).]