Well, I'm not sure if theres a such thing as a free one. But there is a program called Poser that I've heard of, it's an alternative for those expensive 3D programs. Poser I think is $250 about, and I think that is as cheap as they get. Unless you were to get a 3rd party program like Swift 3D, which renders 3D stuff you make into small flash files, but your options are limited with that.
You may also want to try to pick up a demo or trial version of 3D Studio Max(if there is one) or Maya (I know there is one but I'm unsure where).
