It is free to sign up and it allows the creation of 3D models. I can see how this would be great for teaching about properties of shape, angles, actual 3D models, spatial awareness etc. You can export the file as an .obj or a .stl and print these out on a 3D printer. When you add the shape to the 'plane' you can view this object in all directions, resize etc. There are rulers to help with measurements. Great for geometry, angles, measurement etc.
Here is an example of a peg and the beginning of a name plate. To get the 'holes' in the shape, you create the shape you want for the hole, put it over the first shape and then click on 'hide' then group both shapes together and the 'hidden' shape makes the hole.
We also looked at software called Sculptris by Pixilogic. This is free software and is 3D modelling with 'clay' in effect.
It is really easy to use and I could see how this could be used to create characters in narratives, or even worlds, planets, mountains etc.
Here are a few pictures from my result of playing, the original shape being a sphere.
