Johns Hopkins University
The Electromagnetic Spectrum
NASA related site shows the entire Electromagnetic Spectrum. Provides a brief description of the expansive colored spectrum as well as a related link that provides more details.
NASA
Nasa: Imagine the Universe: Welcome to the World of Multiwavelength Astronomy!
This Imagine the Universe site provides an introduction into the multiwavelength universe and astronomy. Site provides graphics, links to a quiz, facts on this topic as well as teacher resources.