We all know that Google is more than capable of doing excellent webware for productivity, but isn't 3D design a bit of a stretch?
Google SketchUp for Windows and Mac is a 3D-modeling program of powerful drawing tools that boasts an intuitiveness many design programs fail to achieve. On first impression, SketchUp looks like it sacrificed function for simplicity, but that's not the case. Despite the extremely user-friendly interface, SketchUp offers a high-end range of powerful 3D-drawing tools that let you experiment and play with new designs.
Using basic shapes in 3D space for your outline, you can then extrude those shapes to make buildings, houses, or anything, really. There are a number of methods to build models, all covered by an excellent tutorial when you get started. You can pick from a number of true-to-life textures to simulate wood, concrete, grass, and several others. When your model is finished, you can save and print it, or you can even place it on a map in Google Earth.