SketchUp, currently in beta stage, is an application that allows you to create your own 3D objects, color and texture your designs, use real-time shadowing effects and grab from a large library of pre-configured objects to add to your design. And as is always the case with most of Google's software, it is completely free.
There is also a commercial version called SketchUp Pro 5 which has a host of additional features, but you may want to take a stab at the free version first to see if it's suitable for your needs.
Bookmarks