Blender is a free, opensource 3D modeling software, available for all operating systems, including Linux based systems.
The software itself is very powerful, and very flexible. I had the opportunity to use Blender in a game development class I took as an elective in college, and within a semester, my class was able to put together a very simple 3D game, with some coding and basic models/animations.
As with most 3D creation software, it has a steep learning curve, but I found the interface intuitive after several sessions of use.
If you are a blooming 3D animation artist and would like to start working on projects without shelling out big bucks for software, head on over to the website and check it out.
Blender Website: http://www.blender.org
Here is an animated short film "Sintel" made entirely with Blender by volunteers of the Blender Foundation:
Enjoy, and live free!