It's Elemental - flash cards to review the elements
Human Body Visual Reference - interactive site about human anatomy
Mad Sci Network - "the laboratory that never sleeps" - search everything science, and if you can't find it, you can ask a scientist 24/7
Molecular Expressions - photo gallery from optical microscopes
NASA - official website
NASA Quest - NASA's website for education
Periodic Table of the Elements - interactive periodic table
Royal Society of Chemistry - promotion, support and celebration of Chemistry
Scientific American - science news and articles from the publication
Weather Underground - find weather information for anywhere