I use the program 'Blender 3D', it's not professional (though used by a few companies). It's VERY lightweight (only 5MB or so, but there's more in it than you'd expect!) and there are a few nice video-tutorials on the net to get started. I used to be a 3dmaxxer but I like the ease of Blender very much.
It can be used for games, 3d-modelling and animation. Very worth checking out.
Oh and BTW., it's open-source
www.blender3d.org
There's some nice modelling in the 'peugot contest':
http://blender3d.org/cms/Peugeot_Contest.493.0.html