Take a look at World's Best Cat Litter (WBCL). I've tried a lot of alternative litters, and I thought they were all crap (sorry) until I saw this one at a cat show. We bought some and it really works. It clumps like crazy, it's biodegradeable, flushable, nontoxic, non-dusty, non-smelly, never gets muddy, and it's chemical free. Our cats really liked it, but it's not easy to find around here. We finally ordered a 58-lb box from
http://www.stuffweuse.com/ and I'm graudually phasing it into our litter robot.
Keep in mind that 58 lbs of this stuff is supposed to last as long as 250-400 lbs of clumping clay litter. That means fewer trips to the pet store, and no more broken backs trying to carry 30-lb pails of clay up the stairs.
I apologize if this sounds like a commercial.

I really do like the stuff, but obviously some cats will not take to it. It also occasionally has a slightly sweet corn odor that some people may dislike ... though it never smells like urine. I do recommend trying at least one small bag.
One of our friends will be trying this litter with the Omega Paw unit. We'll keep everyone posted.