Google Sketch is a famous 3D sketch program which is distributed free by Google Inc. This program is an easier to use than other 3D program. In fact, it's mainly for use with 3D Home Design, which is similar to AutoCAD in usage. But this Google application is really a free one. You can also buy a more professional version of Google Sketch which has more features.
Google Sketch is also very rich in 3D modelling which you can download from the internet, from furniture to character objects, even super heroes like Spiderman.
Here's a short and simple tutorial video on how to draw a simple 3D house with Google Sketch.
