I'm not aware of any free rigs specifically for Carrara. I think one of the reasons why is because the rigs are actually so easy to make in Carrara! ;) If you have Carrara 5 Pro, you can import BVH rigs, delete the motion keyframes and then use it if you'd like. Additionly, with a little effort, you can separate an imported rig from a Poser file if you'd like. Mark