American Association of Physics Teachers
Com Padre Digital Library: Open Source Physics: Inferior Ptolemaic Model
This simulation offers an illustration of Ptolemy's orbit for an inferior planet.
Wolfram Research
Wolfram Science World: Ptolemy (Ca. 100 Ca. 170)
A very brief description of Ptolemy's role in researching astronomy. Links to related information.
Other
The Ptolemaic Model of the Planetary System
An easy-to-read description and history of Ptolemy's geocentric model of the universe. Geocentric means that Ptolemy believed the Earth was the center of the universe.
Other
Nine planets.org: Ptolemy
This site from the University of Arizona provides a background of Ptolemy's profound influence in the areas of astronomy, geography, and cartography. Includes good pictures and related links.