American Chemical Society ChemCenter
http://pubs.acs.org/journals/aoc/aoc_search.html
This page provides a search of the 30 journals published by the American Chemical Society.

Chemicool Periodic Table
http://www-tech.mit.edu/Chemicool/index.html
Interactive periodic table.

ChemInfo (Chemical Information Sources)
http://www.indiana.edu/~cheminfo
"A Chemistry Web guide that brings together all of the useful Web sites at Indiana University with significant chemical information content."

Chemistry Virtual Library Resources: Links for Chemists
http://www.liv.ac.uk/Chemistry/Links/links.html
An index of over 8,350 chemistry resources on the web.

NIST (National Institute of Standards and Technology) Webbook (physical properties for thousands of substances)
http://webbook.nist.gov
A portal to the data collections providing access to a plethora of information compiled by National Institute of Standards and Technology.