Relativity on the World Wide Web . A nice collection of sites on explanations, visualizations, and observational evidence for relativity theory, with emphasis on scientific accuracy. Fundamental Physical Constants from NIST . The current list of the values of constants used in physics and astronomy. Unit Converter .
Site provides conversion between a variety of physics-related units.
One of several sites that provide the facts behind the supposed planetary alignment in May, 2000. Bad Astronomy . Lots of misinformation related to astronomy are addressed at this site. What to see in the sky. Sites with material on what is viewable in the sky.