Sketchup
by Google
Google SketchUp is software that you can use to create, modify and share 3D models. It's easier to learn than other 3D modeling programs, which is why so many people are already using it. We designed SketchUp's simplified toolset, guided drawing system and clean look-and-feel to help you concentrate on two things: getting your work done as efficiently as possible, and having fun while you're doing it.
