If you need a free and powerful 3D application then maybe trueSpace is the tool for you. trueSpace goes way back as a commercial application, but last February Microsoft bought Caligari (the creators of trueSpace), and last July they released the full version of the app as freeware!
The big idea seems to be that they’d like people to use it to provide content for Virtual Earth, Microsoft’s version of Google Earth (Google released Sketchup as freeware, too – see the parallels? ;-).
Included in the download are a whopping 51MB of documentation and 132MB of video tutorials to get you going. Impressive.
The only thing that’s NOT included in the freeware version is the renderer V-Ray, which is sold separately for $299.