Biological Sciences
Howard Hughes Medical Institute
HHMI is a nonprofit medical research organization which employs hundreds of biomedical scientists who are helping to enhance science education at all levels.

General Science
National Science Foundation (NSF)
Official government site for the National Science Foundation whose mission is to promote the progress of science, to advance the national health, prosperity, and welfare, and to secure the national defense. contains reliable resources selected by 12 science agencies. Selected authoritative science Web sites and often hard-to-access scientific databases are provided.
A Science Odyssey
A Science Odyssey takes you on a journey through the most spectacular 100 years in the history of science and technology. This web site is a companion to the PBS television series.

Provides calculations and/or conversions of measurements, money and time.
Mathematicians of the 17th and 18th Centuries
Provides accounts of the lives and works of seventeenth and eighteenth century mathematicians (and some other scientists), adapted from A Short Account of the History of Mathematics by W. W. Rouse Ball (4th Edition, 1908).

Physical Science
Atlas of Rocks, Mineral and Textures
This site provides a good beginning to building a resource for introductory petrology organizing images of plutonic, volcanic, and metamorphic microtextures with links to other related minerals or textures.
Eric Weisstein's World of Physics
Provided as a public service by Wolfram, this site features 12 areas of physics, each with a large number of subsections. There are also links from this site to chemistry, astronomy and mathematics
How Volcanoes Work
This web site describes the science behind volcanoes and volcanic process. It is intended for the education of university students of geology and volcanology and teachers of earth science.