For a good 3D modeling program, try Blender3D.
http://www.blender.org/It's free and updated quite regularly by a community of 3D modeling programmers.
You can model, render, whatever. Even has a new "sculpting" technique.
I've been messing around with it for a few weeks and haven't gotten proficient in its use yet, but there are lots of tutorials posted for using it, one of the best being: Blender3D: Noob to Pro
http://en.wikibooks.org/wiki/Blender_3D:_Noob_to_ProThis program is also good for "modding" object for a lot of 3D computer games.
I've also heard good things about some programs call Milkshape and Wings3d (both supposedly free) but haven't tried them, so I don't know how they will work.