http://physics.nist.gov/PhysRefData/Elements/index.html NIST Chemical Element Data
http://webbook.nist.gov/chemistry/ NIST Chemistry WebBook
http://www.vanderkrogt.net/elements/index.php Elements dictionary and name origin of chemical elements
http://www.chm.bris.ac.uk/motm/motm.htm Molecule of the Month. "Each month a new molecule will be added to the list on this page. The links will take you to a page at one of the Web sites at a University Chemistry Department or commercial site in the UK, the US, or anywhere in the world, where useful (and hopefully entertaining!), information can be found about a particularly interesting molecule."