Free searching of passenger lists for people coming into New York.
http://libertyellisfoundation.org/passenger
Starting in 2001 the JFK Trust began to compile a most comprehensive database of Irish emigration to the United States, in conjunction with the Balch Institute in Philadelphia, the Ellis Island Restoration Commission in New York and the Battery Conservancy in New York. Access to the database is free through this website. Printouts are available for a small fee
http://www.dunbrody.com
This site offers enhanced searching of a range of different online databases. There are also translating tools and resources on the holocaust.
http://stevemorse.org
This website has details of people who became Mormons and emigrated to the United States. Most are European, especially British, but some are from Australia and New Zealand. Information is taken from immigrants' accounts and passenger lists.
http://lib.byu.edu/mormonmigration
This site has over 10,000 searchable passenger lists, mostly for people emigrating from Britain to the United States.
http://immigrantships.net
Searchable database of immigrants entering the United States 1830-1892. This pre-dates the Ellis Island immigration database.
http://www.castlegarden.org
Searchable database of immigrants to the United States commemorated on a wall of honour. They can have arrived in the US through any port.
http://www.wallofhonor.com