I know that I've mentioned to a few close friends and family members, as well as the vet, that we have decided to train Doozer to use the toilet. It's not so much that cleaning out the box is a hassle (it is, but I'll do it) as it is that Doozer is very clumsy in there--stepping in his business and tracking it into my bed. Doozer seems to be a very bright cat and is always very interested in all the goings-on in the toilet, so we figured he'd be a good candidate for this process. I've adapted it slightly, but I think it will still work.
Step one: wherein the toilet is filled with cat litter (and the cat is intrigued):
He declared that this was a fantastic idea: