My sequential art teacher introduced this website to us and I wanted to share the wealth with all of you who may be interested. The greatest feature about this site, is that it demonstrates the movement of the muscles in the face in order to get from one expression to the next (great tool for anyone in animation). Anyway, here is the link:

http://www.artnatomia.net/uk/artnatomy.html

Hope you guys find it as useful as I found it to be :).

Fascinating stuff Niel

thanks! This is going to be very helpful!!