Another one to look at is Cubify Sculpt, from 3D systems: http://cubify.com/sculpt. It has a "virtual clay" interface that's easy for kids to grasp, while it's powerful enough to create highly detailed and solid models suitable for 3d printing. The Cubify series of products are 3DSystems' big new idea: creating more accessible versions of much more expensive software (and hardware) products, so that users can create their own content and have something to do with their 3D printers.

Andrew Werby
www.computersculpture.com