Hi there cbriggs! Welcome to Pettalk!

Baking Soda, Baking Soda, Baking Soda!
That's the best smell-absorber I have found.
You can buy kitty-litter w/ baking soda in it. In my humble opinion, the 'multiple cat formulas' work best. Also, covered litter boxes (if you can get your cat to use them) work wonders on reducing the smell. (We have one cat that will use it and one that won't. )

We also keep one of the glade-plung-in thingies next to the boxes.
Hope this helps!!