I can't remember what it was called, but I loved the stuff I got at Wal-mart.
It was white, and really really light. It came in a plastic container and smelled like oranges.
It dehydrates the poo, and even though I lived in a tiny tiny one bedroom house with 3 cats I couldn't smell anything (except right after they pooed. That -always- stinks.)
I think it was like 9 bucks for the container, but it would last my 3 cats for about a month. I would pour the whole thing into the box and then just scoop it daily and mix the litter stuff around.
I'd also just use the container to dispose of the poo and once the litter was all dirty, put it back in the container and that's all the clean up I had with it.
I think it was some sort of clay or something. I can't remember now. But I love it. And once I get my kitties, I'll definitely be using it again.
Damn, I wish I could remember what it was called though....