I use a cutting board.
On a side note, DON'T get a RadPadz. I had one, and LOVED it right away. It was so slick and accurate.. Problem is the damn thing wore out. All the little bumps in the middle started to smooth down (where I move the mouse the most) and so it became VERY inconsistant. That is a bad thing.
Click here for a pic of my worn out RatPadz GS. In the pic it looks like it is dirty, but it isn't. It has actually worn smooth from using it so much. Of course, I do play a lot...
Then go to
http://www.ratpadz.com/ to see what a new pad looks like. All the little bumps wore away. Notice around the edge it is still bumpy like it is supposed to be, but serverely worn out in the middle.
And the worst part is it wore out in just a few months. I love the pad but I am not going to buy a new one every three months, so I got a cutting board instead.