I have my table sited on a granite slab which basically is very rigid. In addition, I have found that putting DH Squares under the turntable feet dampens it further and makes the playback more musical.
http://cgim.audiogon.com/i/vs/i/f/1052207936.jpg
http://cgim.audiogon.com/i/vs/i/f/1052207936.jpg