Just got to know about Google SketchUp, a powerful 3D modeling software. It is quite simple and easy to learn.
Have fun creating 3D models of buildings, vehicles, etc. depending on your creativity and imagination. You can also add detail and texture to your models.
After you are done, you can place the models using real-world coordinates and share them with others on Google Earth using Google 3D Warehouse.
Google SketchUp 6 is FREE while Google SketchUp Pro 6 costs $495/