To eliminate tracking, (my babies are super messy!), I picked up an artificial turf welcome mat at the hardware store and put their litter box on it. It looks like plastic grass, but you can get it in alot of different colors and sizes. Does a great job of cleaning their little paws and it's easy to shake out. They have something similar at Petco, but as usual it costs about 4 times the price.

Don't get me wrong, I love Petco. But, I gotta go where the bargains are!