Moviesandbox now allows you to create your own characters and animations, including your own skeleton setups and physics based animation.
Once you created your own bone structure, you can skin your object by drawing on it, as seen in this video:

bone weighting and skin deformation from Friedrich Kirschner on Vimeo.

I actually use a .tga file created in photoshop for the vertex information, ao all my characters are point based. but you’re free to import collada objects as well (including skeletal information).

Also, you can create physics bodies. I am using ODE as physics engine and you can connect multiple physics objects together using a variety of joints. And then skin them, just like regular bones in a skeleton. Here’s an example:

ODE Physics test from Friedrich Kirschner on Vimeo.

Again, the actual vertex information comes from a .tga file.
It’s all a bit abstract, but that’s okay for me…