If your wanting to get into 3D modeling and animation, but want to use an open source program, I highly suggest using Blender.
http://www.blender.org/Click on Gallery to see some stuff created with it.
Blender Cookie is a great site with free tutorials. Plus, for $10 a month you get access to exclusive "Citizen" tutorials. And they are well worth the money.
http://cgcookie.com/blender/
Another great site for learning Blender is Blender Guru.
http://www.blenderguru.com/
And for free downloadable Blender magazines with tutorials and articles check out BlenderArt Magazine.
http://blenderart.org/
The software has come a long way since it's original clumsy interface was updated. I dismissed the program back before version 2.5, but now I can't seem to learn all the features they keep adding to it. It opens the door to those of us on a tight budget, because of the software itself and also because of the great tutorials available.