We saw these at Home Depot last week (though the one pictured is from Target...I couldn't find the one we saw online):
I'm not in the midst of potty training or anything, but when I head down that road again, I may be back to pick up one of these. There is an extra seat built right in...just perfect for a child-sized bottom. I guess they've been around for a few years, but I've never seen one.
Is that great or what?