Other
Fear of Physics: Albert Einstein's Theory of Relativity
Fear of Physics uses animations and simple language to teach the theory of relativity.
Wikimedia
Wikipedia: The Black Hole
This site examines the black hole as an object in astrophysics. Delve into this comprehensive resource that covers this concept from its history, to qualitative physics, the reality of black holes, mathematical physics and more.
American Museum of Natural History
American Museum of Natural History: O Logy: Stuff to Do: Views From Windows
Instructions that take you through an Einstein-like thought experiment by having you imagine and record what you see when stationary and when moving at the speed of light.
Other
Einstein Archives Online
Online access to portions of Einstein's original papers and manuscripts.
Stanford University
Stanford Univ/gravity Probe B/relativity Q&a
Click "Relativity Q & A". Over 200 questions and answers dealing with relativity (special and general), answered by NASA scientist Dr. Sten Odenwald. Answers are generally one paragraph, very clear and coherent.
Other
Quantum Mysteries: Deepening Quantum Mysteries
Although it is arguably the most successful theory in physics, quantum physics has often baffled and confounded both its practitioners and the general public. This informative website discusses the types of mysteries, which still plague...