Rosie is partially trained to use the litter box - which means she uses it only when she's in the crate. She still hasn't got the connection that when she's running around the house free that she should run back into the crate and use the litter box. <sigh>
I went to this website which I found really helpful.
http://www.kturby.com/litter/litter.htm
I think the lady who wrote the article owns italian greyhounds (the miniature greyhounds which are almost adorable as chi's!)
I use Yesterday News litter (think it's a Purina product) which I pick up at Wal-Mart (convenience). It is recycled newspaper pellets. I read somewhere that the clump-able cat litter could be dangerous if the dog ingests it as it would clump in their digestive system and sometimes has to be surgically removed. Ack!
We also have a 1.5 year old cat (Scooch) that has her own litter box which is in a separate area from Rosie's. She did try to use it once, but we just loudly sound "No Scooch" and she ran away and hasn't tried it again.
The litter is also different for the animals Rosie open litter box with pellets and Scoochie's closed litter box with clumping litter.