Here are two ways to keep plain kitty litter smelling fresher and cleaner:
1. (Submitted by a reader) Sprinkle baby powder in the litter every time you change it.
2. My favorite tip - I sprinkle baking soda in the kitty litter every time I change the cat litter box. It helps to neutralize odors SO well, and it's natural so it's safe for my pets. :)