Algodoo

a horsheshoe orbit involves a main body (white) which is orbited by (usually) large and small satellites that kind of play tag, but never touch. This is because of the acellaration the larger object on the smaller one. It pulls it faster in its orbit, causing it to move to a higher orbit, causing it to move slower until the massive object moves around the planet and meets the smaller object again, pulling it slower, which drops it to a lower orbit, making it go faster until it loops around the planet and meets the massive object again.

Feel free to suggest more orbit ideas!