Ancestors On Board is now online. The site states:
Passenger lists with over 30 million records from ships sailing to destinations
Findmypast.com, in association with The National Archives, has opened ancestorsonboard, a new database featuring 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. Images of the passenger lists are available to download, view, save and print.
You can search many passenger lists to the US including Ellis Island, Castle Garden, and other ports at
Immigrant Passenger Lists
Passenger Lists Database Searches to USA