The best and most expensive programs out there would have to be: 3ds Max (the best in my eyes), Lightwave, Maya (one used in Matrix i believe). On the free side there is: Gmax (very good, used it before passing to 3ds Max), Wings 3d (tried it but never gave it a deep look), Anim8or ( quite good and rather easy to use once you have read the tutorial and can make rather good biological shapes and it has a rendering engine) There you go there are many out there. Up to you to try them and find the one you prefer. I think Maya actually exists in a free version.