Blender is one of the free multi platform 3D software like MAYA. It have Windows, Linux, Mac os X, Solaris and FreeBSD version of software. You also can get the source code of the software. Interesting right.
Sample movie created/edited/rendered using blender:
Big Buck Bunny
[youtube]YE7VzlLtp-4[/youtube]
Elephants Dream
[youtube]bsGEWHNJ3s8[/youtube]