4 links
April Fool's Day
thefoolsday.com
Includes hoaxes, pranks, gag gifts, trivia, history, quotes, messages, funny party ideas and April Fool recipes.
Infoplease.com: April Fool's Day Has Serious Origins
infoplease.com
Relates the serious origin and history of this light-hearted day.
Snopes.com - April Fool's Day Origins
snopes.com
In-depth look at several of the legends that surround the origins of the holiday. Includes some modern day examples.
Wikipedia - April Fool's Day
en.wikipedia.org
Hyperlinked encyclopedia article includes the day's origin and information on well-known hoaxes.