http://www.sketchup.com/

At SketchUp, we do our best to make great tools for drawing. For our users, drawing is thinking. They draw to explore ideas, to figure things out, to show other people what they mean. They draw because they love it, and because nothing great was ever built that didn’t start with a great drawing.

3D Warehouse:

https://3dwarehouse.sketchup.com/

3D Warehouse contains millions of models created in Sketchup, the world most popular 3D modeling and design application.