BioLinks - A collection of links from the Molecular and Cellular Biology Dept. at Harvard University; note the sections on biochemistry and biomolecular databases.
Chemdex - An outstanding collection of resources from the University of Sheffield.
Chemical Information Sources Wiki - Wiki on searching, and writing for chemistry -- a textbook in Wiki format, from the outstanding School of Informatics at Indiana University
Chemie.de -- A German website (in English!), particularly strong for company and product info. Provides RSS feeds if you want to be updated on new content.
SIRCh: Selected Internet Resources for Chemistry -- Another Wiki style collection of useful resources for chemistry. Note especially the list of chemistry blogs, newsgroups and discussion lists!
Wendy Warr & Associates Links page -- A collection of links from the website of Dr. Wendy Warr, renowned chemistry journalist and chemical information specialist. Other pages at the site have excellent coverage of cheminformatics and combinatorial chemistry developments.
WWW Chemistry Guide - a collection of links to over 270 resources, grouped into categories