- Clockworks from Sundials to the Atomic Second
- From Encyclopedia Brittanica, this site offers an animated exhibition explaining the sundial, clepsydra, astrolabe, candle clock, sandglass, weight driven clock, spring driven clock, pendulum clock, quartz watch, and cesium atomic clock.
- Solar Pictures
- This collection of pictures is a useful companion resource for classroom investigations of solar energy.
- Photovoltaic Cell Introduction
- This is just a short video clip, but it's a nice illustration of how photovoltaic cells work. It was created by the U.S. Department of Energy.
- Pictures of Sundial
- This site lists links to hundreds of pictures of sundials around the world. While the variety is amazing, they all work on the same basic principle.
- Historic Sundials
- While much smaller, this site also features a collection of photos of sundials. The Franklin Institute has a unique collection of historic sundials.