ASciFi.com: The Science Fiction Forums: Message boards for a variety of series, including Farscape, Stargate, and X-Files.
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.
Coffeerooms(sm): Jolau's Sci Fi Board: A gathering place for friends and fans of science fiction television.
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.
Othala: Multi-fandom forum with threads for Stargate SG1, Stargate Atlantis, Red Dwarf, and Manifest Destiny.
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.
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.
Xena and Hercules Universe: Science fiction, fantasy, and fan fiction message board.
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.]