A long long time ago, I bought three mouse mats. I'm still using them. They are the Fellowes 91741 Mouse Pad
The front of the mouse mat has a gel pad for resting your wrist on; that helps to prevent RSI. The back of the pad is a good sized surface - my Microsoft optical mice work very well on it.
They are, of course, more expensive that the freebie rubbish that many people give away as promotion items. I looked around, the best price I found was £13, but if you don't have a decent mouse pad, and do a lot of mousing, I'd recommend one of these.
But the surface on which the mouse glides gets dirty. Today, I took action.
I took all three of them down to our laundry room, and scrubbed the surface with a nylon scrubber and detergent. Rinse, dry and now they're as clean as the day I buoght them, and probably good for another 20 years.