Sketchup is a pretty amazing product, especially since you can download the non-pro version for free. It's utilized by millions of people to do 3D modeling with especially loyal followings in the engineering, architecture and construction industries for obvious reasons.
SketchUp was originally created by @Last Software. Their team got to know Google while developing the Google Earth Plugin for SketchUp, which allows crowd sourced construction and mapping of 3D buildings and non-flat earthly features. They had been selling their product for $500 a pop, but Google decided to release a free version along with the now...