NCI Drug Dictionary
nci.nih.gov/drugdictionary/

Drug Bank
http://www.drugbank.ca/

IUPHAR: data base of receptors and Ion channels
www.iuphar-db.org/index.jsp

In the pipeline: a medicinal chemistry blog
pipeline.corante.com/

The Binding Database: binding affinities of drug targets with small, drug-like molecules
www.bindingdb.org/bind

ChEMBL: a database of bioactive drug-like small molecules
www.ebi.ac.uk/chembl/

PubChem
pubchem.ncbi.nlm.nih.gov/

Binding MOAD: protein crystal structures with relevant ligands and binding data
bindingmoad.org/

GRAC: guide to receptors and channels
www.guidetopharmacology.org/

PDBbind database: experimentally measured binding affinity data
http://sw16.im.med.umich.edu/databases/pdbbind/index.jsp

Therapeutic Targets Database: provides information about known therapeutic protein targets
http://bidd.nus.edu.sg/group/cjttd/TTD_HOME.asp