Yahoo! Chemistry Listing
A wide variety of chemistry links from Yahoo! Further investigation required.

chemistry.about.com

Chemfinder - chemical structure information of thousands of molecules - works well if you have generic names rather than trade names.

ChemExper Chemical Directory -The ChemExper Chemical Directory, an online database of fine chemicals, contains 60000+ compounds together with their physical properties such as boiling point, melting point ... as well as IR spectrum (5000+), MSDS (12000+), supplier information, 2D and 3D structures.

ChemDex - lists all the Departments and Chemical companies in the world

Liverpool - lists all above and more