Advent Children Unlimited
Fan page offers plot and character information, screenshots, wallpaper, magazine scans, and trailers.

Advent Children: Final Fantasy 7 Movie (FF7AC Movie)
Features pre-FF7AC trailers download, searchable image/screenshot galleries, movie reviews and analyses, and a large number of fan works (trailer, music video, dvd).

AdventChildren.net
Offers the latest news, screenshots, fan works, and articles relating to the movie. Also includes discussion forums and a chat room.

Final Fantasy Hybrid - Advent Children Source
Contains news and basic information on the movie.

Final Fantasy Insider
Offers general information, storyline, characters profiles, images, movies and wallpapers on the movie.

Final Fantasy Net - Advent Children
Provides speculation, cast information, character biographies, interviews, story lines, and trailers.

Final Fantasy Shrine
Provides general movie information with screenshots and trailers.

Final Fantasy Ultima
Contains screenshots, videos, wallpapers and basic information regarding the movie.

GameSpot
Features editorial news stories, previews, images, videos, FAQs and a forum.

IGN
Basic background information about the movie with news coverage and media (trailers and screenshots).

IMDB
Contains cast and crew details, movie format information, plot summary, trailers, goofs, quotes and a message board.

RPGamer
News articles and collected media.

Square Enix - Final Fantasy VII Advent Children
The official site containing news, story, character information, trailers, wallpapers and merchandise for North America.

Wikipedia
Collaborative online encyclopedia (wiki) page that provides extensive motion picture information and backgrounds.