IMDb: Magnum P.I.
Cast bios, crew details, user comments, quotes, trivia, and production information.
http://www.imdb.com/title/tt0080240/

Magnum Episode Guide
A comprehensive list of all the episodes of the tv series, with synopsis and sounds.
http://www.8ung.at/ralffrank/Magnum/magnum.html

Museum TV: Magnum, P.I.
Facts and trivia about the series with Tom Selleck.
http://www.museum.tv/archives/etv/M/htmlM/magnumpi/magnumpi.htm

Yahoo! Groups: Magnum P.I.
Show, cast, character, and episode discussion. [Yahoo! registration required.]
http://tv.groups.yahoo.com/group/Magnum_PI/