This move from Brooke Burke-Charvet works your butt AND legs.
Here's how to do it: Start on hands and knees, with hands under shoulders and knees under hips. Extend right leg out to right side as straight as possible with toe pointed and touching the ground. In one fluid motion, move right leg in an arc motion, up then over until right leg is diagonally behind left, with right toe on ground. Reverse arc motion to start. Repeat for 30 seconds on one side, working up to a minute.
Try this move: Rainbow