PubChem (http://pubchem.ncbi.nlm.nih.gov/) is a great public repository of screening data. So far I have been downloading selected data by hand via the webinterface, not too hard to do but not high throughput or very convenient either. PubChem have recently added a PUG (Power User Gateway) SOAP interface, which automates this process. The good news is that example PP components are provided, see http://pubchem.ncbi.nlm.nih.gov/pug_soap/examples/pipel.../pipeline_pilot.html.