Di-O-Matic has a great interview with Luis San Juan, character rigger with Nexus Productions, fresh off their latest commercial for the International Olympic Committee. In it he discusses the process of facial rigging as well as various software tools used.
We used another tool, created by Matt Clark one of our fellow freelancers at Nexus, which allowed a good fast automatic skinning for a starting animation and proxy version of the mesh. (Sliced mesh linked to the rig for having a quick frame rate). The skinning was improved later and we used skin morph to model correction shapes where we needed in the models, mainly hips, elbows, knees and wrists.
Later we focused on facial rigs. I prefer a nice UI that makes animating easier, so the UI we used was a mask to select controls for the eye brows, the jaw, lips, lip corners and animate them as you would move them in reality. So if you grab a lip corner and move it on the side it will move the corner of the mouth to the side. I like each icon to be quite graphic so the user is not confused with what he is grabbing.
