Chemistry

• Chemweb 

Chemical & Physical Properties

• Knovel E-Books
• CRC Handbook of Chemistry and Physics
• NIST Chemistry WebBook
• MatWeb
• ChemFinder
• Beilstein Crossfire 
• SciFinder Scholar

General Reference

• Grad School Shopper
• Nobelprize.org
• Periodiques
• Telephone numbers
• Zip Codes

Lesson Plans

• Cornell Theory Center Math and Science Gateway
• Educators' Reference Desk
• Materials World Modules
• Newton's Apple
• PBS Teachers' Source 

Materials Sciences

• Materials Science
• Materials Science Resourses on the Web 

Physics and Astronomy

• Alloy database
• comPADRE
• find sounds
• Finding Property Data
• intute
• IOP Constants and Equations
• NIST Solubitity Database
• The United States Naval Observatory

Professional Societies

• American Association for the Advancement of Science
• American Astronomical Society
• American Chemical Society
• American Institute of Physics
• Astronomical Society of the Pacific
• Institute of Physics
• The National Academies (US)
• Royal Society of Chemistry

Publisher Templates

• American Association for the Advancement of Science (Science)
• American Chemical Society
• American Institute of Physics
• American Physical Society
• Elsevier
• Nature Publishing Group
• Springer
• Taylor & Francis
• World Scientific

Publishing

• Copyright
• Style guide --chemistry
• Style guide --general
• Style guide--physics and astronomy 

Scientists

• Interview Gallery at the National Academies
• Women in Science, Health and Technology

Web Searching

• Search Engine Showdown