Daz Studio - FREE (Interface for 3D rendering)
http://www.daz3d.com/i/software/daz_studio3

FREE Models and other objects.
http://www.daz3d.com/i/3d-models/free-3d-models?cat=382

Other software (not free)::
Bryce, landscape design.
http://www.daz3d.com/i/software/bryce

Hexagon, create models from scratch.
http://www.daz3d.com/i/software/hexagon

Carrara, photo-shop for 3D models.
http://www.daz3d.com/i/software/carrara

Poser, like Daz studio, but commercial based (I think it sucks, but others like it)
http://poser8.smithmicro.com/dr/index.html