ChemFinder
Search for information on over 17,000 common chemical compounds by chemical name, CAS Number, molecular formula, or molecular weight.
Chemistry.org
The web site of the American Chemical Association
Elemental Data Index NIST
Image and tabular information on periodic table elements.
Household Products Database NIH/NLM
Health and safety information on household products.
National Institute of Standards and Technology Chemistry WebBook
Detailed information on chemical compounds.