I've already posted some HHGG fan sites, here are the offical sites.
Touchstone Pictures Official HHGG Movie Site has trailers, characters, gallery, games, wallpaper and Marvin the Paranoid Android to guide you through. Requires Flash.
The BBC has been presenting the HHGG for many years on both TV and Radio and has lots of material online.
BBC Hitchhiker's Cult Site - Photos, Screen Saver, Quizzes, Douglas Adams and another version of the Guide.
BBC Radio 4 Hitchhiker's Guide - Game, Game Hints, Picture Gallery, Message Board and the Radio Cast.
The official site of Douglas Adams, the Hitch Hiker's Guide to the Galaxy author.
