Physics 

• American Institute of Physics
• American Physical Society Guidelines for Professional Conduct
• APS Research Journals--home of Physical Review, Physical Review Letters, and Reviews of Modern Physics.
• Center for the History of Physics Newsletter
• Contributions of 20th Century Women to Physics
• Galileo Galilei's Notes on Motion--electronic representation of Galileo's manuscript Ms. Gal. 72
• High Energy Physics Experiments OnLine
• HyperPhysics -- an excellent source, a real must. 
• the Internet Pilot to Physics (TIPTOP)--is reputed to be "the world's most comprehensive index to online physics resources." 
• Laws List--an alphabetical list of laws and principles in physics and astronomy
• MetaPhys: the Physics Document Search Engine
• Multimedia Images -- from the University of Washington.
• Multimedia Physics Studio--with animations and gifs demonstrating velocity, acceleration
• National Geophysical Data Center--basic climate, geophysical and environmental data from National Oceanic and Atmospheric Administration.
• Net Advance of Physics-- Encyclopedic entries, lecture notes, review articles
• NIST Physical Reference Data
• Physics and Astronomy reference -- "a comprehensive physics and astronomy online education, research and reference web site."
• Physics Flash Animation -- animations are sorted by category, and the file size of each animation is included in the listing. Also included is the minimum version of the Flash player that is required.
• Physics Frequently Asked Questions
• Physics Web--from the Institute of Physics Publishing Dept.
• PSIGate Physical Sciences Information Gateway -- provides access to high quality internet resources in physical sciences, including research, statistical data, news, articles, etc.  Searchable.
• SciCentral's Gateway to Physical and Chemical -- "gateways" to sub-disciplines, to databases, research reports, educational materials, conferences, employment, funding
• Science.gov --a gateway to authoritative selected science information provided by U.S. Government agencies, including research and development results.
• The Science of Particle Physics--courtesy of the Fermi National Lab, an introduction, including a glossary of terms.
• Virtual Physics Laboratory--must be able to support JAVA applets
• Visual Quantum Mechanics
• Visualization applets of various concepts in math and physics
• A Walk through Time -- designed by the NIST Physics Lab. It shows the progression of the measurement of time throughout human history. 
• Web Pages To Help Physics Students
• WebTOP -- is a 3D interactive computer graphics system that simulates and visualizes optical phenomena.