The Official Call of Cthulhu RPG Homepage:Chaosium's CoC RPG web page has the official information for the game and supplements, as well as useful downloads, fiction, news, and links.
Berkley Cthulhu Archive: A collection (somewhat dated) of mailing list archives, character sheet templates, character generators, pictures and other miscellaneous items. Most of the material dates from 1993-1996.
Byakhee: Windows WYSIWYG computer program, investigator generator for any era and Delta Green, prints telegrams. Free, download source code.
Call of Cthulhu Adventures Online: 3 by Michael C. LaBossiere: My Aunt's House, Drooler in the Dark, The Knife.
Call of Cthulhu d20 Character Sheet: Preview and download a new character sheet (.pdf) to use with the d20 Call of Cthulhu RPG system.
CoC CharGen: OpenSource character generator written in Java. Released under the GNU GPL.
Cthulhu Coffee: A slightly humorous website that has information about the Cthulhu Mythos and various convention parties the owners throw.
Cthulhu Dark Ages: A supplemental website for the Call of Cthulhu roleplaying game, setting the clock back 1000 years into the middle ages.
CTHULHU International: CTHULHU International provides support to Call of Cthulhu RPG and its Pagan Publishing Supplements; Delta Green, players and Keepers and to promote the writings of H.P. Lovecraft.
Fallen Future: Cyberthulhu Gaming: A cyberpunk-genre rules expansion and adventure for the Call of Cthulhu RPG.
Javascript Cthulhu d20 Character Generator: A rather hefty client-side script which can take a while to load on Internet Explorer.
Mook's Mythos Madness: Call of Cthulhu, Cthulhu Live, Lovecraft and Cthulhu Mythos art and props site. Prop making techniques and larping discussions
Propping up the Mythos: A guide to making objects from the stories of H.P. Lovecraft. Resource for making props for Call of Cthulhu or Cthulhu Live games.
Scooby Doo Cthulhu: Will the horror never cease? Stats for the 5 cartoon characters in CoC format. Jinkies!
Shoggoth.net:: An interactive weblog, forum, and article archive for the Mythos & Call of Cthulhu RPG Community. Current and updated often.
Tales of Terror: A collection of grisly ideas for use in Call of Cthulhu and other games. Each Tale is a short horror scenario description, "stripped clean of rotting statistics and wretched prose", a paragraph or so, with three alternate Possibilities for developing the events behind the mystery.
The Mana Bros Call of Cthulhu Pages: Resources, including the regularly updated "Turin (Italy)Guidebook" for 1920s, short Lovecraft bio and Italian Publishing History, Book of Characters: professions and generation rules (MSWord Zip); Niteside Dreams, alternate setting for Call of Cthulhu games using Film Noir conventions in a magic-rich world subtly corrupted by the Mythos.
Unseen Masters: Official site for the "Unseen Masters" adventure supplement for Chaosium's Call of Cthulhu Role Playing Game.
Vampulhu!: Conversion rules and design outline for a Vampire: the Masquerade / Call of Cthulhu hybrid RPG under White Wolf rules.
Yog-Sothoth.com: Also known as 'CthulhuFan.com', this web site is dedicated to Chaosium's game, 'Call of Cthulhu'. Roleplaying in the worlds of H.P. Lovecraft.