University of Toronto (Canada)
University of Toronto: Visualization of Pectoral Motion
Provides information and illustrations about the role of pectoral motion in fish locomotion.
University of Florida
Florida Museum of Natural History: Ichthyology: How Fish Swim
Provides descriptions and illustrations of how fish swim.
Other
Look D: How Fish Swim
This site, which is provided for by LookD.com, gives brief but factual information on the way in which fish swim.