From Chemical Abstracts Service, a free look-up for CAS Registry Numbers of approximately 7,800 chemicals of widespread general public interest.
Directory of Graduate Research
Searchable online version of the American Chemical Society's Directory of Graduate Research, providing information on graduate programs at universities in the United States and Canada.
IUPAC Gold Book
Compilation of chemical terminology from IUPAC (International Union for Pure and Applied Chemistry).
The Photographic Periodical Table of Elements
Interactive table with images
The Periodical Table of Videos
Periodic table with video clips of descriptions of elements, from chemists at the University of Nottingham (UK).