I bought a really cool thing at Archiver's called the Double Stamp Scrubber and a little spray bottle of stamp cleaner. You spray one side of the scrubber with the cleaner, then rub your stamp on it so it "suds" up a bit, then you rub it on the dry side. There are little fibers that really get in there and clean them up, even the ones DDs have abused. Here's a link to one online:
http://www.stampin.com/online/accs/miscacc.htm#scrubber