Other
Black Holes and Neutron Stars
Contains information about black holes and neutron stars: how they form, what they're like, and how we know they are there.
PBS
Newton's Apple: Black Holes
This site from Twin Cities Public Television contains great information from a program called "Newton's Apple" concerning black holes. Contains activities for viewers to try to emphasize points related to black holes. Topics include:...
BBC
Bbc: Wormholes
The BBC reveals what is known about wormholes, a possible consequence of Einstein's Theory of General Relativity in which space is bent, opening up the possibility of time travel.