Just found this thing on the Fresh Step litter's box about some kind of rewards points program that they have. I got my first 50 points! They actually have some useful things that you can get with your points, like a Cat First Aid Kit. a book called "50 Ways to Pamper your Cat" and a rolling cat carrier (it's like 1000 points but hey, it looks good).
And of course, free litter with enough points. That can be priceless for us since we're still on a tight budget.