Second Daughter started really and truly jumping on purpose over the weekend. Both feet off the ground at the same time. It would be more impressive a post if I had a video of it, but she doesn't stay in one place very well (nor does she perform by request).
She also jumps from one piece of furniture to another and from furniture to the carpet, but usually only if she thinks we're not watching. The older two, of course, either ignore or encourage this behavior.