PBS
Pbs Learning Media: The Beginnings of the Telescope
This animated essay from the NOVA Web site examines the design of Galileo's refracting telescope and Sir Isaac Newton's reflecting telescope.
Other
Meade Instruments Corporation: How Telescopes Work
This page explains in fairly simple terms the basics of telescopes. It includes information on the various types of telescopes and the factors people use to select the correct telescope for them. Meade is a leading telescope manufacturer.
University of Wisconsin
The Why Files: Terrific Telescopes
Why? File provides insight into four advances in telescope technology as well as shows how they are "improving our harvest of cosmic understanding."