I've just been browsing through the NAR Database issue whilst the the historical focus was on molecular biology resources the current issue contains over 500 resources that would be of interest to drug discovery. In addition to well known databases like ChEMBL, PubChem BioAssay and RCSB there are many others. A few that caught my eye:

TransportersDB Database of membrane transporters
SureChEMBL Annotated patent database
canSAR Cancer research and drug discovery knowledgebase
iPPI-DB Modulators of protein-protein interactions
Withdrawn Withdrawn drugs
Open Targets platform for therapeutic target identification and validation