Science Struck
Science Struck: How Does Light Travel Through Space and Other Media?
A detailed discussion of the nature of light, how it can travel through a vacuum, and how the speed of light is affected when light travels through a medium.
American Museum of Natural History
American Museum of Natural History: Ole Roemer and the Speed of Light
This resource provides a concise overview of the speed of light and the Ole Roemer, the first man to measure it.