* Photo Match – Users can now quickly and easily trace a photo to create a 3D model of the photographed object or match an existing model with a background photo for near-instant modeling.
* Styles – New collections of display settings including Watermarks (2D images behind or in front of models) and Sketchy Effects (rendered as though drawn by hand) enable users to create 3D models to fit their professional or personal needs.
* 3D Text – Users can now convert text to 2D outlines, filled surfaces, or extruded 3D objects.
The program is free (there's also a commercial version), works in Windows and Mac, and has a lot of tutorials. But most people will need them only for the basic concepts, as the software doesn't need too many explanations.
You'll discover some building models if you open Google Earth 4 (which is now out of beta), go to the Layers section, and enable 3D Buildings / 3D Warehouse.