This looks even more fun! It's a Ripstik caster board, which only has 2 wheels and moves by you rocking your feet in opposite directions, so you don't have to push off the ground. From reviews online, most people say they like it a lot(and the users range from little kids to working adults), except that the wheels wear out very fast. It looks difficult to learn how to use it though, but most people say they can pick it up reasonably fast. Plus it looks cool :D. It's more expensive than a Soleskate though, and seems to be more for riding for fun than for commuting.

Oh yeah, FYI, the Soleskate is $26 and the Ripstik is $50 if you buy it online, much cheaper than if you buy it on site.