Where to Find 3D Files?

Group,

I am considering making the plunge with a 3D printer add on to one of my cnc-mills.

Looking for 3D models.

Specifically I'd be interested in a good 3D model of the lost in space robot (B9), Robby the robot, R2D2, C3PO, etc.

Anyone know of any good websites for artistic downloads?

Thanks!

Joe