Have you visited the Google 3D Warehouse lately? It now showcases Featured Google Earth Modelers. This area includes "photo-textured models of georeferenced (located in the right spot in Google Earth) buildings that are developed with efficiency in mind, creating the most beautiful result with the least amount of polygons as possible."
Which is a fancy way of saying that these folks have created extremely cool 3D models for your viewing pleasure. One of my favorites is this collection of buildings in Pakistan. I am also fond of this series of bridges.
Want to build you own 3D models? Download Google SketchUp 6. The product features some great video tutorials.