Pass the Sketchup

For those of you who like to build virtual models, the free version of Google Sketchup is an "easy-to-learn 3D modeling program that enables you to explore the world in 3D. With just a few simple tools, you can create 3D models of houses, sheds, decks, home additions, woodworking projects - even space ships. And once you´ve built your models, you can place them in Google Earth, post them to the 3D Warehouse, or print hard copies."

I personally downloaded this one, and while I definitely need to watch all of the tutorials it seemed a bit more friendly than Blender. I also like that you can access galleries of models built by other users and download them (and don't quote me on this, but I'm pretty sure you can even modify them to suit your needs.)