Information about Einstein's theories of special and general relativity and their applications; site is hosted by the Max Planck Institute for Gravitational Physics. Includes a simple introduction, a collection of articles ("Spotlights on relativity"

Video clips and lectures about cosmology, particle physics, relativity and quantum mechanics presented by string theorist, Brian Greene. Requires free registration.

Discusses the nature of energy and matter in its relation with space-time, its relation with relativity, and unified strengths.