Jason Osipa's book "Stop Staring" is something of a bible to facial expressions.
Since Jason is quite familiar with Animation:Master and several of the examples in the book are straight out of A:M I'd like to suggest that.
Anzovins have several CDs worth of tutorials on modeling and rigging a face.
Definitely worth the price of admission. Bill Young and Justin Barrett are the authors I believe.
Free resources of good quality are harder to find but do exist.
Since rigging is in your future you definitely should grab David (Itsjustme) Simmon's Rigging a Face tutorials from the Software Tutorials Forum. There are other rigging tutorials but they don't focus on the face... still useful though so yell if you run out of resources.
Grab Rich (Entity) Jackson's realist model from the extra CD content. That is a good study.
While perhaps more stylistic DO NOT forget to study the work of Jim Talbot.
If nothing else you'll want to study his use of decals.
Lets see... where to next... Lipsync?
Gary C. Martin (A:M Master of long ago) has some great tutorials on his website.
We'll see what other resources we can come up with... there is a lot out there.
Good luck on your research and your project!