Long before the age of "Trains, Planes & Automobiles, the ship was the way to travel. The vast majority of immigrants arrived on foreign shores using this mode of transportation. Luckily for the genealogist searching for their roots, most ports kept detailed arrival and immigration records. A boon to the researcher and carrying a wealth of information.
Ancestors On Board - search for passenger list 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. Searching is free but their is a fee to view complete documents
Canadian Geneaology Centre - hosted by Library & Archives Canada this site includes lists for ships from 1865 - 1935 and much more
Immigrants To Canada And Ships They Came On -The data in the following tables was extracted from the Government of Canada Sessional Papers, Government Immigration Reports (GIR), and passenger list records
Irish Immigration Through The Port Of New York - this site identifies 604,596 persons who arrived in the Port of New York, 1846-1851, and the ships on which they arrived
Olive Tree Genealogy - Search for your ancestors in free Ships' Passenger lists, Naturalization Records, Palatine Genealogy, Canadian Genealogy, American Genealogy, Native American Genealogy, Huguenots, Mennonites, Almshouse Records, Orphan Records, church records, military muster rolls, census records, land records and more
The Ships List - includes passenger and immigration lists and records
What Passenger Lists Are Online? - a good source for research. Heavy on American content but does include some other countries