There are many databases that identify and describe chemicals and drugs. A select list of databases below can be searched by chemical common or trade name, CAS Registry number, molecular formula, structure... when appropriate.
A directory and source about all-things-drugs including regulations, alerts and data. Browse drug classifications or by generic, trade or chemical name.
ACS small molecules database for searching and property data. Includes chemical registry, reactions, structure and identifier searching, requires a unique username/password.