I suggest using Blender 3D because its a good program for 3D Modeling and Animation and it has a Game Engine in it to make your own video games, This is the only "Free" 3D Modeling/Animation program that I know and you can get it off their site. http://www.blender.org/ and its really worth downloading.
If your interested in other programs I suggest using Maya, 3Ds Max, and Lightwave and all of these are 3D Modeling Programs and Animation programs but you will have to download trials and they are really expensive.
When ever you get the money and if your still interested in 3D Modeling and Animation I suggest getting 3Ds Max because its the best program they have so far and Maya is a good one also so as Lightwave 3D Because The Adventures of Jimmy Neutron was created in Lightwave 3D