What seems like a long time ago I wrote rigarmarule in Blender 2.49. For reference you can check the blog post here and here , or you can check out the project from SVN:
svn co http://projects.freefac.org/rigamarule
Rigamarule is not exactly an auto-rigger (though it can be part of one, or assist one) – it’s rather better thought of as a constraint system that affects rigging instead of animation. To make it easier, we call them ‘rules’ rather than constraints, and it makes sure things in your rig stay aligned and correct no matter how you move the joints around. This allows making fast adjustments to characters, or it allows retargeting a rig to a different proportion character, or it can be used to make templates ‘smart’ for use with etchaton or other template-retargeting system (at which point you do get something like an autorigger)
The problem is that this system was written in Python 2.5 / Blender 2.49. At the time we hadn’t switched the movie to Python 3.1/ Blender 2.5. Our script is now not usable by us! and I do not have enough time budget to do the porting myself.
This is an official cry for help, if we can get some assistance porting we can use the script for the movie, and it will allow future upgrade work to make the script even better, and to further integrate it with other rigging tools to help make the ultimate autorigger for Blender.