Astro Gate Forums - Message board with topic threads including Andromeda, The X-Files, and Stargate: SG-1, as well as discussion of science and science fiction in general.
Fantastic Television - Message board and chat room for fans of science fiction and fantasy shows.
Flare Science Fiction Forums - An old, large Star Trek-turned-Sci-Fi community seeking new members. Formerly known as the Starfleet Communications Relay and the Behaviour Group Forums.
The Fringe Posting Board - Discussion forum for fans of anime, Buffy the Vampire Slayer, Angel, Babylon 5, Highlander, Stargate SG-1, and The Tomorrow People. Includes polls and fan fiction.
Othala - Multi-fandom forum with threads for Stargate SG1, Stargate Atlantis, Red Dwarf, and Manifest Destiny.
Psi Fi - Discussion board with threads on shows including Andromeda, Enterprise, Psi Factor, and Buffy the Vampire Slayer. Also offers discussion on space and science news, as well as tape trading.
PsiProne's Sci-Fi Nexus - A Sci-Fi, Fantasy and Horror forum, includes special help forums for webmasters.
Tigerclaw's Crossfire - Fans debate burning issues such as whether Imperial Star Destroyers from Star Wars could defeat Star Trek's Galaxy-class starships in combat. Includes polls and a variety of message boards.
Yahoo! Groups: Sci Fi Junkies - Message board for fans of Stargate SG-1, Enterprise and The Dead Zone to discuss how much they enjoy watching the shows. Includes photos and polls. [Yahoo! registration required.]