I use Arm&Hammer Super Scoop, unscented when I can find it, though I don't mind the Fresh Scent and neither does Bella. When I refill the box I just sprinkle a little baking soda on the bottom, and sometimes if I remember I'll mix some in when I top off the box, too.
I convinced a friend to try the Yesterday's News for his ferret, and I was so impressed with the difference in odor levels I may switch myself at some point when I'm a bit more solvent
I HAD to get a cover litter box because I had a three-foot radius around the "framed" litter box that was, pardon the pun, littered with the clumping stuff. For such a little cat she's got great range when she's throwing that stuff!
Thankfully, though, she uses the covered box w/the odor filter for her poo, and the framed box which is now on linoleum for pee, so unless you're in the bathroom with the box, you wouldn't even know I have a cat (unless of course, you trip over one of her furry mice!)