http://fantasticcontraption.com/

It's an online physics puzzle game called "Fantastic Contraption". The goal is to build a machine that will move an object across the playing field to a target area to win.


Solutions can be simple, like below:



Or you can make crazy machines that get the job done:



It's really a rather clever game, and it's perfectly free (although you can buy a $10 "full" version which gives you the ability to design your own levels and share them with others. Still, there are plenty of levels in the free version to challenge people.)