NIST Physical Reference Data
http://physics.nist.gov/PhysRefData/
Nobel Prize in Physics
http://nobelprize.org/nobel_prizes/physics/
Optical Society of America
http://osa.org/
http://physlink.com/
Physics Central
http://physicscentral.com/
Physics on the Web
http://www.physics.org/
PhysicsWorld from IOP Publishing
http://physicsworld.com/cws/home
Science Accelerator
http://scienceaccelerator.gov/
Select Sources from the Library of Congress
http://www.loc.gov/rr/scitech/selected-internet/physics.html
SPIRES
http://www.slac.stanford.edu/spires/
US Goverment Science Information
http://science.gov/