Chemdex An excellent site with hundreds of links well worth visiting.
Chemistry Classics This excellent site has selected, classic papers from the history of chemistry, including many which were seminal papers in their fields in their time.
Oxford University's Molecule of the Month A site which features a new molecule every month, featuring historical, chemical and pharmacological background information.
Protein Data Bank Besides being ainternational sourec of structural data on proteins, the PDB has a Molecule of the Month with structural and other information.
General Chemistry Online A very useful site with tutorials on a range of basic topics. There is also an 'Exam Survival Guide'.
Plastics Resource This site contains much information about plastics with features on recycling.