University of Colorado
University of Colorado: Physics 2000: Einstein's Legacy: X Rays
An explanation of how X-ray machines work. An online activity in which a comparison is made between how the hand would be viewed with X-ray versus with visible light. An additional page explains the use of X-rays in CAT scan devices.
Emory University
Emory University: Something About X Rays for Everybody
A summary of a century of research regarding X-rays. Discusses the discovery and applications of X-rays. Includes some ideas for exploring and investigating X-rays.
University of Colorado
University of Colorado: Physics 2000: X Rays
Here's a really simple demonstration of a fluoroscope. There are links to more information about the uses of X-rays as well.