Round and round the Stargate goes, where it stops, nobody knows!
This is the long Stargate link list. Thanks to Jerie and Jade for many of the links.
I recognize a few names from Voyager fandom, like CGB and SuzVoy. Helpful fans have also recommended Alli Snow, Denise (for good Teal'c), Doc (sight unseen), Sally Reeve, Seldear, and Sue Corkill. Several of these authors work on The Gate Review, a fan fiction review site.
Stargate is on the air Mondays and Fridays on the SciFi Channel. Yes, you can watch it on TV. MGM and the SciFi Channel have official sites. See also Richard Dean Anderson and Amanda Tapping's sites.
General Stargate information can be found at Gateworld and Abydos Gate. Arduinna's Stargate SG-1 Handbook and The Stargate Compendium provide encyclopedic detail. SG1 Web has nitpicks. The mythology of Stargate is recorded at The Truth Behind Stargate SG-1.
Transcripts of the show are available at moon-catchin.net and stargatefan.com, and there's even a Yahoo mailing list where you can get them hot off the presses. Stargate Nebula has some quotes. TVTome/Epguides has an episode guide.
SuzVoy has really short episode recaps and Five Minute Voyager exo-hosts Five Minute Stargate.
For cartoons, see Sevgate Sev-1, and Kitty's Cartoons. Pink Khaki defies description.
There's a nice write-up of the Stargate glyphs at rdanderson.com. Glyph fonts are available all over the place. (This page's design is based on the fixed background trick from css/edge using three small png tiles made with the earth glyph.)