123D Make allows you to do the impossible, which is make 3D objects with a laser cutter. It has many options of how the parts can be assembled and even numbers them for you!! The interface is easy to use and there are a lot of options.
Watch this demo of how it works!
People have made some really amazing stuff with it!
Do not worry if you can not get your hands on a laser cutter, 123D Make will even teach you origami.