TinkerCAD (www.tinkercad.com) is an online tool that gives users the opportunity to design custom 3D models, for free! These designs can then be exported for 3D printing. Unlike other CAD programs, TinkerCAD is very easy to learn and uses a simple three-step design process.
Help Using TinkerCAD
TinkerCAD.com provides great starter walk-throughs, lessons, and projects for beginners.