This is what I believe James Cameron should have done with that Na'vi Boobs.

This is a computer generated lady running naked without a bra. Her large natural boobs are just jiggling all over the place.

If Jessica Alba had a boob job, she might look the girl in this animation. I'm still trying to figure out how to make Jessica's boobs bounce by themselve, but I haven't had any luck. I'm using poser 8 to modify the Alyson character in the face room to make her look like Jessica Alba. The render time was around 3 hours for this animation. I thought about using Maya 10, or Cinema 4D, but why re-invent the boob, when I can just use Poser.

Here is a video of the Alyson Character rendered in Poser Pro 2010. I used dependent parameters to make the breast move. I edited the hip x,y, and z rotation parameters and linked them to the breast morphs using the start teaching tool.