A good source for displaying emotions in 3-D characters in the book "Stop Staring: Facial Modeling and Animation Done Righ" by Jason Osipa (ISBN: 0782141293 $32.99 @ Amazon.com). Smiling pretty much involves your whole face. Your nose wrinkles up a bit, your lower eyelids wince a bit, the groves at the sides of your mouth deepen a lot and you mouth does go out and up. The book has a great section on getting eye poses to look natural, too.