I use brass cones, 2.25"-thick maple cutting boards, and rubber/cork pads underneath all components (cones directly underneath the component on top of the boards...pads between the boards and my shelf)...honestly don't know if this results in less vibration or just different vibration, but I really like the effect it has had on my system. I've experimented a little, and I've found that using these things had the most sonic effect with my amp (I would have thought the biggest effect would have been under the cd player/transport, but not so)...
I'm also looking into trying out some Symposium Svelte Shelves under my speakers, although that's about a month away...