You can get the free Personal Learning Edition
, that's supposed to be fully functional to Complete 6, just watermarks your renders, and I believe they removed plug-in support, and limited the rendering capabilities.
Another free alternative to a commercial software is Gmax
. I think
it functions identical to 3ds Max, minus particles, and it doesn't support rendering stills or animations... however you can do some searching, and people have figured out a way to get it to render by exporting the data from it's listener window, to an xml file, and then using external rendering software, like Povray.
Or, you can go the totally free route, that looks damned impressive from what I've seen of it (haven't had much time to tinker with it yet, beyond just basic stuff), Blender
. Used to be a commercial product produced by an animation house that went out of business, so the product eventually got released in open source. No watermarks, no limited rendering (or dissabled rendering).