OpenCorporates: open access database of the corporate world.
Site launched in order to increase accountability and access to data about companies. It provides listing of companies links to their websites and to public government information about them. This includes Vat registration, financial statements, UK health and safety notices, records in the UK gazette and notices of awards of government contracts. Currently data is held on over 3 million companies (mainly from the UK) but more is being added daily. Information on sources and methodology is available on the website.