Moira, who will be two in January, is potty training herself. It started one morning when she came into the bathroom stark naked and I put her on the potty until I could get a diaper back on her. She peed, and I made a big deal about it (of course). Since then she LOVES going potty on the toilet. On Saturday she threw a fit every time we took her off (cuz we had things to do other than sit and watch her grin on the toilet, no matter how cute it is). I got out the little training potty, which allows her to go potty herself, which she does. She went upstairs tonight and went poop- without even telling me.
We're still working on things like wiping and getting clothes back on (she can take them off just fine). But she is seriously potty training herself. Such a crazy kid!