Below are a few recommended websites. Remember that information you find on the web needs to be evaluated carefully. For more information on evaluating websites, check out the Evaluating Sources Research Guide.
ChemDex
http://www.chemdex.org/
The Sheffield ChemDex is regularly updated and contains over 5000 links to chemistry resources on the internet.
ChemGuide
http://www.chemguide.co.uk/
Designed to help students understand the concepts of chemistry.
ChemID Plus
http://sis.nlm.nih.gov/chemical.html
Database of over 375,000 chemicals, synonyms, structures, regulatory list information, and links to other databases.
Chemical Information Sources
http://en.wikibooks.org/wiki/Chemical_Information_Sources
Compilation of online chemical information resources.
Chemistry Resources on the Internet
http://guides.library.ucsb.edu/chemistry
Annotated list of good, free chemistry sites.
Chemicool
http://www.chemicool.com/
History and various information dealing with chemistry and, in particular, the periodic table of elements.
ChemSpider
http://www.chemspider.com/literaturesearch.aspx
ChemSpider is a free-to-access collection of compound data from across the web, provided for the benefit of the community by the Royal Society of Chemistry (RSC). It aggregates chemical structures and their associated information into a single searchable repository and makes it available to everybody.
Classic Papers in the History of Chemistry
http://web.lemoyne.edu/~giunta/papers.html
Compilation of links to historical papers.
General Chemistry Online
http://antoine.frostburg.edu/chem/senese/101/index.shtml
Provides notes and guides for the first semester chemistry student.
Merlot Chemistry Portal
http://chemistry.merlot.org/materials.html
Learning materials available for chemistry students.
NIST Chemistry WebBook
http://webbook.nist.gov/chemistry/
The National Institute for Standards and Technology provides various ways to search standard reference data on chemicals.
Organic Chemistry Resources Worldwide
http://www.organicworldwide.net/
Designed as a reference guide for synthetic organic chenists, this site is structured around the daily tasks of an organic chemist.
PubChem
http://pubchem.ncbi.nlm.nih.gov/
PubChem provides information on the biological activities of small molecules.
Science.gov
http://www.science.gov/
Gateway to government websites dealing with chemistry and other sciences.