Here are a few great tips to keep your cat litter try smelling fresh:
Baby Powder To keep cat litter fresh smelling, mix some baby powder in with the litter - you will just love this fresh scent (your cat will smell good too!)
Baking soda Another thing that will work to absorb the odors in pet litter, is adding baking soda (bicarbobate of soda). Sprinkle some in the bottom of the tray before you put the litter in and it will help to keep things fresh. When you don't have time to change the litter, just pour a little more baking soda in on top of the litter to hold that chore off a little longer.
Borax Blend 6 parts cat litter with 1 part borax before you fill the cat tray. It will reduce the smell of the litter box.