Hille, B. (2001) Ion Channels of Excitable Membranes. 3rd edition. Sinauer Associates, Inc., Sunderland.
Junge, D. (1992) Nerve and Muscle Excitation. 2nd edition. Sinauer Associates, Inc., Sunderland.
Sperelakis, N., Editor. (2001) Cell Physiology Source Book: A Molecular Approach. 3rd edition. Academic Press, San Diego.
One of the most informative, interactive, and at the same time scientifically rigorous web resources related to voltage-gated ion channels and the action potential is developed and maintained by Dr. Francisco Bezanilla of the University of Chicago. Visit this site at: http://nerve.bsd.uchicago.edu/.
Animations for the textbook by Gary G. Mathews: Neurobiology: Molecules, Cells and Systems.
Max Animations provides several nice animations for physiology education.