the hacksaw method works great if you're patient and careful... used it myself.
The idea is to chuck the mount in a vise, slip a hacksaw blade through the inside of the mount, tighten the blade back on the saw, and cut out the majority of the rubber. Then carefully cut the metal sleeve around the original rubber until it gives way. Be careful not to cut into the outer mount. You can then remove the inner sleeve w/ the rubber with a hammer + chisel or whatever.
I'm sure there's a decent writeup about it somewhere. Its pretty straight-forward, and if I can do it, anyone can... /ubbthreads/images/graemlins/grin.gif