External databases
ChEMBL - an open data database containing binding, functional and ADMET information for a large number of drug-like bioactive compounds
ChemSpider - a free chemical structure database providing fast text and structure search access to over 32 million structures from hundreds of data sources
DACS - a database of available chemical substances
PubChem - a database providing information on the biological activities of small molecules
ZINC - a free database of commercially-available compounds for virtual screening