I've already taught Dante how to lay down when I ask him to (mostly because he always used to decide that he was tired of doing what I asked, so he'd just lay down... I started saying "Get down" everytime he started to lay, and eventually he picked up that when I said "get down" he was supposed to lay down... I didn't expect it to work, honestly. ), and Bandit will try to offer his hoof to you if you say "Nice to meet you!" and hold out your hand, but he won't pick it up very high, so it doesn't really work.
I'm mostly interested in teaching my big gelding to lay down, or at least sort of bow, so that I can get on his back a little easier.
I also sort of want to teach Magic and Tanner to bow and rear of command (from the saddle) -- I told one of my friends that if they ever run a great time in barrels, I should have them bow down before they leave the ring, just to be silly.