MakerBot Feet

They're height adjustable to make it easy to level your bot and has a slot on the bottom to add a rubber band or washer of some sort to help cushion it and reduce vibrations and noise.

I'm not sure how much quieter it is, so might need thicker O-Rings on the bottoms.

The holes are tricky to get right so that the nuts and bolts fit snuggly, might need editing for your makerbot skeinforge settings.

They attach to the MakerBot by tightly squeezing and pinching onto the side panel so they're pretty easy to take on and off.

Could also design different bottoms to screw into them. I might try making something like the RepRap Anti-Vibration Feet: http://www.thingiverse.com/thing:808