Dataface: Psychology, Appearance and Behaviour of the Human Face (Joseph C. Hager).
This comprehensive site includes a good facial anatomy section.
http://face-and-emotion.com/dataface/general/homepage.jsp (home)
http://face-and-emotion.com/dataface/expression/muscles.jsp (clickable muscle diagram)
http://face-and-emotion.com/dataface/anatomy/anatomy.jsp (numerous images from 19th and early 20th century anatomy books)
Artnatomy (Victoria Flores).
Interactive demonstration of facial anatomy and expression.
http://www.artnatomia.net/uk/index.html
della Porta, Giambattista, 1586. De Humana Physiognomia.
Not exactly facial anatomy, but too good to leave out.
http://www.nlm.nih.gov/exhibition/historicalanatomies/porta_home.html
Dream Anatomy (US National Library of Medicine).
Two historical images of facial anatomy (in addition to the many other to be found among the works cited on the historical anatomies page).
http://www.nlm.nih.gov/exhibition/dreamanatomy/da_g_II-C-10.html (Albrecht von Haller, 1708-1777)
http://www.nlm.nih.gov/exhibition/dreamanatomy/da_g_III-B-05.html (Jean-Galbert Salvage, 1770-1813)
Duchenne, Guillaume-Benjamin, 1862. Mécanisme de la physionomie humaine, ou, Analyse électro-physiologique de l expression des passions, par le docteur G.-B. Duchenne (de Boulogne). Avec un atlas composé de 74 figures électro-physiologiques photographiées (in French).
http://archive.org/details/Duchenne1862oj91W
Darwin, Charles. The Expression of the Emotions in Man and Animal.