Library of Congress
Loc: Wise Guide: Honor Your Father, at Least Once a Year
The Library of Congress provides information on the origins and observation of Father's Day.
Wikimedia
Wikipedia: Father's Day
Wikipedia's entry on Father's Day discusses the history of the holiday and lists the dates for its occurrence in different countries.
A&E Television
History.com: Father's Day
The History Channel presents a comprehensive look at the holiday of Father's Day. Provides history, video clips, photos, famous TV dads, and more.
English Zone
English zone.com: Father's Day
The origins of how Father's Day became a national holiday are discussed on this site.