When I was first getting into the show, I saw Stargate books on the shelves... but it took me a while to catch on that there were two concurrent series: "Stargate SG-1" (in the continuity of the show) and just plain "Stargate" (following directly on the original movie and ignoring the show altogether). It was a little confusing.
For a number of years now, friends and I have been running a tabletop RPG that's set in the Stargate SG-1 continuity. It isn't Earth-based and the characters have had no direct contact with Earth — but I've done crossovers with quite a few other elements from the show. (So far the setting has progressed between about 1995 and 1998.) The Tok'ra have had a regular presence with a few appearances by Martouf, Jolinar, and Anise. I featured the backstory of Anubis' ascension, the backstory of the monk on Kheb, and how the Tok'ra knew to go looking for Setesh on Earth. One of Machello's anti-Goa'uld gadgets, a new type, has appeared. The Atanik armbands showed up briefly (before the Tok'ra became aware of them). Harlan and the android SG-1 have appeared ... in fact, our adventurers were duplicated before SG-1 was, but Harlan couldn't get those duplicates to work.
Zipacna and Ra showed up a few times (and Ra's death at the hands of the Tau'ri made the news). We had a plotline with an Asgard who was cut off from his people while doing research on clone degeneration. Since we all know how that turned out, I had him make contact with the Vanir in the Pegasus Galaxy and give his research to them instead. Recently I featured how Col. Cromwell survived the fall into the black hole. Cromwell has turned into a pretty popular NPC.
Next a solar flare is going to gate the characters 5000 years into the past where they'll team up with the alternate SG-1 from "Moebius" to fight Ra. (The alternate O'Neill didn't have his run-in with Cromwell in that timeline, so the two of them are going to have their argument for the first time again.) When that's over, it will give the alternate SG-1 a chance to go home.
