Available Chemical Databases?



 Dear Netters,
 Stimulated by the discussion about the NCI database I would like to
 compile a list of all available chemical databases. I would like to
 know about free and commercial databases with any kind of chemical
 information and structure representation/registry-number.
 Since I believe that most people are interested in the compiled
 list please reply to me, I will summarize the answers to the list.
 Thanks Alberto