You can download and try out the rig here:
[7/14 Note:  This downloadable rig has been discontinued and replaced with the improved practice rig.  New turning rig coming soon!]
 
This rig was created with help and inspiration from
 
Daniel Gies’ amazing work and tutorials
everyonediesfilms.com
 
Duik tools v13.0.2

PuppetTools v2.3
 
Thanks for additional coding help from
 
Joe Russ at Mografi
mografi.com
 
Dan Ebberts at the Creative Cow Forums
forums.creativecow.net/adobe_after_effects_expressions