Herein please find some of the fanfiction sites that I frequent to find some good Stargate SG1 stories. Just to warn you, I am a Daniel Jackson fan so most of the sites and stories I read are centered around Daniel or Daniel and Jack with minor emphasis on Team oriented stories.
WARNING/Disclaimer: Some sites do have adult content! I've tried to tag these as such but I might not know all the sites linked here thoroughly so watch out if you are young or this is not your cup of tea!
Some other sites I frequent in no particular order:
Annie's page~Adult content
Devra's and JoaG's Page~Adult content
Has one of my favorite stories of all time "Dream of Minnesota" please be aware it is slash and thus heed the warnings!
Great Daniel and Jack friendship stories and great vids! One of my favorite places on the web! Spend tons of time there with the Ancient Obsessions List!
Stargate Fiction Recommendation site: I spend tons of time here - looking for stories I would never find otherwise! Check it out. I do rec there sometimes under the username dmk0064
The Alpha Gate ~ A great archive of Stargate Fanfiction with both general and slash stories. Heed all warnings. I do archive my stuff here as well.