Taken directly from ancestorsonboard.com:
Findmypast.com, in association with The National Archives, is proud to present ancestorsonboard, a new database featuring BT27 Outward Passenger Lists for long-distance voyages leaving the British Isles from 1960 right back to 1890.
With ancestorsonboard, you can search for records of individuals or groups of people leaving for destinations including Australia, Canada, India, New Zealand, South Africa and USA featuring ports such as Boston, Philadelphia and New York. Passengers include not only immigrants and emigrants, but also businessmen, diplomats and tourists. Images of the passenger lists are available to download, view, save and print.