SketchUp is a free 3D modeling program, which was acquired by Google in 2006. It has been designed as a 3D modeling program that's easier to use than other 3D modelling programs. A key to its success is its easy learning curve compared to other 3D tools.
Mac OS X, Windows XP, and Windows Vista operating systems are supported by this program that can be downloaded from http://sketchup.google.com/. Although there is a commercial SketchUp Pro version available, the free version works fine in conjunction with Papervision3D.
An interesting feature for non-3D modelers is the integration with Google's 3D Warehouse. This makes it possible to search for models that have been contributed by other SketchUp users. These models are free of any rights and can be used in commercial (Papervision3D) projects.