DCFutures: Hellblazer - Several fan fiction stories about John Constantine.
Hellblazer Home Page - A Hellblazer discussion board, fan fiction, and an incomplete index of John Constantine appearances.
John Constantine's Friends and Family - Brief text descriptions; current through issue #8.
Ravenscar's Hellbalzer Page - Quotes from the comic and an index of magic John Constantine has performed.
Sailor Hellblazer - A Sailor Moon/John Constantine crossover fan fiction.
Straight To Hell : A HellBlazer Site - Information on John Constatine: Hellblazer, with focus on the characters and the stories. Also, a small gallery and some interviews.
The Ultimate Hellblazer Index - An index of appearances by the Vertigo character, John Constantine, and his relatives and alternates selves, both in his own title, Hellblazer and in other comics.