Directories & Gateways

• Materials Science Resources on the Web (article from 'Issues in Science and Technology Librarianship')
• ChemBioFinder is an online chemistry and biology reference database. With more than 500,000 compounds cataloged and linked to
  other web sites, it provides a wealth of chemical information for professional chemists and students alike. ChemBioFinder.Com serves as the gateway to all
  database offerings from CambridgeSoft.
• ChemWeb is a portal providing access to full text journals (fees payable), structure searching, Beilstein Abstracts, web resources, job news, conference news.
  Requires registration.
• Chemdex is an internation directory of Chemistry resources on the internet
• chemsoc - the Chemical Societies Network - information from over 30 national chemistry societies, news, weblinks, online magazine, conferences and events
• Organic Chemistry Resources Worldwide
• Intute: Science, Engineering and Technology a UK directory of internet resources for teaching, learning and research, covering the physical sciences, engineering,
  computing, geography, mathematics and environmental science.
• TOXNET (Toxicology Data Network): from the US National Library of Medicine provides access to a range of databases giving toxicity data and references to the
  toxicological literature, including:
• - Hazardous Substances Databank (HSDB)
  - Integrated Risk Information System (IRIS)
  - TOXLINE (extensive references to the literature)

Organisations

• American Chemical
  Society (ACS)
• Royal Society of
  Chemistry (RSC)
• see Chemdex's directory of Chemistry organisations listed by country
• American Academy of Forensic Sciences
• American Society of Crime Laboratory Directors
• American Society of Questioned Document Examiners
• Association for Crime Scene Reconstruction
• Association of Firearm & Toolmark Examiers
• Justice Info Technology Network
• National Academy of Forensic Engineers
• Society of Forensic Toxicologists
• Australian Institute of Criminology
• Australasian Legal Information Institute- AUSTLII
• National Institute of Forensic Science

Resources

• ChemPort - comprehensive list of journals available via the web. Provides links to journals on publishers' websites which then give limited access (typically tables of contents and abstracts) and require payment for access to the full text of the articles. 
• Ausforens - Australian Forensic Sciences Discussion List
• Forensic-Evidence.com
• Forensic Firearms Identification
• Forensic Science Resources in Criminal Fact Investigation

Reference

• Periodic Tables of the Elements - there are many interesting web versions
  available: for example WebElements and the Periodic Table of Comic Books

• The Wired Chemist: a collection of Chemistry resource