Tinkercad is a free-of-charge, online 3D modeling program that runs in a web browser. Since it became available in 2011 it has become a popular platform for creating models for 3D printing as well as an entry-level introduction to constructive solid geometry in schools.
Recent launches
TInkercad
TInkercad is an easy to use web app that lets you virtually play around with an arduino. It's easy to use and since you can code with blocks. It's fast and easy to get your projects started.