SketchUp is a 3D modeling program with a fairly robust free version. They’ve added quite a few features and the one that caught our eye in particular was dynamic components.

Revit families are converted into components and tagged with the name of the family category (i.e., walls, floors, windows, furniture). Entities in Revit are imported as SketchUp components.

@Last Software today announced the availability of free SketchUp Component Libraries for use in the film and stage, interior design, landscape architecture, architectural and mechanical design ...

Google 3D Warehouse is a central portal where anyone can contribute 3D components for SketchUp users. SketchUp is also noted for its integration with Google Earth.