Base Peak
Formerly "Mass Spectrometry on the Internet", an index page of mass spectrometry internet sites including links to mass spectrometry groups, companies, resources, and software.

Chemdex
Directory of chemistry on the WWW since 1993.

Chemistry Directory
Liverpool University based list of chemistry links.

Chemsoc
Online networks in specialist areas, science, industry and product news, a comprehensive events database, job centre, access to major references, and society resources.

ChemWeb - online Club for the Chemical Community
Owned by Elsevier, requires registration. Features searchable chemistry journals and databases, jobs, books, software, conferences diary and ChemDex+.

Top20Chemistry.com
Online directory for chemistry education in organic, analytical, bio, physical, electro, atmospheric, and several other topics.