The Ellis Island records site, which contains 25 million ship passenger records covering 1892-1924, has relaunched with some new features.
New features include an enhanced range of data fields, additional information on Ellis Island, and information on famous people who arrived in the US via Ellis Island.
The National Archives and Records Administration has a genealogy section that lists all their databases. Some are online, others are at a research center. The Northern California Federal Records Center has census records and passenger arrival records from 1893-1957.
A mindboggling aggregate of genealogy sources can be found in Cindi’s List.
Signup for a free 2 week trial at Ancestry.com to search the actual Census records, which are available to the public only through 1930.