April Fool's Day: Features old postcards, a brief history, and traditions.
April Fool's Day or All Fool's Day: Features a brief history of the holiday.
Celebrate Holidays in the USA: April Fool's Day: Tells how people in the United States celebrate April 1.
Infoplease.com: April Fool's Day: Relates the serious origin and history of this light-hearted day.
The April Fish Day Story: Yet another version of how the observance began.
Urban Legends Reference Pages: April Fool's Day: An in-depth look at several of the legends that surround the origins of April Fool's Day.