This redstone thingy is simple, but not that easy to build actually. What it does is that the slime blocks make you bounce around in a square - so, you get pushed upside 4 times, and sideways 4 times. Not really easy to explain though, you should just download it. Also, this doesn't always work, so I recommend you to stay as close as possible to the button (the one you click to start).

Requires snapshot 14w18a or newer.