Eureka Alert is a Global source for Science News published by the American Association for the Advancement of Science.
Khan AcademyProvides free videos and practice exercises for many subjects, including Chemistry, Mathematics and Physics.
Provides 100 videos illustrating aspects of Physics: Classical mechanics, Electricity and Magnetism, Fluid Mechanics, Optics, Quantum Mechanics, Relativity, and Waves
Claims to be the web's most extensive free mathematical resource.