General Science

Life Sciences

Physical Sciences

Dictionaries and Encyclopedias

• Dictionary of Algorithms and Data Structures NIST
• Dictionary of Geologic Terms
• A Dictionary of Units
• A Short Dictionary of Scientific Quotations
• Encyclopedia of Earth
• Geology Dictionary Geology.com
• Glossary of Energy Terms
• The Laws List a list of various laws, rules, principles, and other related topics in physics and astronomy.
• The Mathematical Atlas
  A collection of short articles which provide an introduction to the areas of modern mathematics and pointers to further information.
  
• The Rainbow of Gems : An Encyclopedic Treatment of Basic Gem Information
• Eric Weisstein's World of Mathematics
  A comprehensive and interactive mathematics encyclopedia intended for students, educators, math enthusiasts, and researchers.
  

Tables

• Engineering Technical Data Reference Tables
  A listing of engineering reference data commonly found in reference books.
• The Foot Rule - Unit Conversions
• Fundamental Physical Constants NIST
• Interactive Units Converter
• Math Reference Tables math2.org
• Periodic Table Live!
• Periodic Table of the Elements WebElements.com
• Mathematical Tables and Formulas S.O.S. Math

Databases and Information Resources

• Astronomical Data Center, NASA
• ChemFinder : Database and Internet Searching
• Search Hazardous Substances Hazardous Substances Information System, Australia
• Material Safety Data Sheets - Where to Find Them On the Internet
• MatWeb - The Online Materials Information Resource
• Mineralogy Database
• NIST Data Gateway
  Provides easy access to scientific and technical data from the US National Institute for Standards and Technology (NIST). These data cover a broad range of substances and properties from many different scientific disciplines.
  
• NIST Ceramic WebBook

Bibliographic Databases

• Scirus
  is a science-specific search engine covering over 105 million science-related pages. It searches both free and journal sources.
  
• USPTO Patent Bibliographic and AIDS Databases