Black Holes: Gravity's Relentless Pull

An absolutely amazing webpage. You can search for black holes in the sky using a variety of telescopes (x-ray, visual, radio), travel through space at impossible speeds (like thousands and millions times the speed of light) to different types of black holes (solar-mass and supermassive), and conduct a variety of experiments (exploring stable orbits, the distortion of light and time around black holes, and much more). There is also a Black Hole Encyclopedia with more in-depth information. The webpage won the top prize in the 2005 Pirelli INTERNETional Award competition, which recognizes excellence in communication of science and technology on the Internet. Guaranteed fun.