sga_santa started going live on Sunday, and I wanted to share some of my favorites. My recs are all McShep, but note that there are stories with other pairings (including het) as well as gen stories, so even if you don't do slash, check out the community for stories that might be more to your taste.
Stargazing by ??? - If you're at all into classic science fiction (Asimov, Clarke, Heinlein, etc.), this is a must read. It's the best kind of future!fic there is, and in terms of SGA AUs, I've never seen one done better. The author created a hell of a world, and like a lot of other readers, I would love to see more stories set in this particular 'verse.
Like A Coin by ??? - The life and loves of Rodney McKay, starting from age 5. I love the character voices in this, and I adore the Rodney McKay presented by the author.
Forever Home by ??? - John and Rodney are stranded with no real way home. Like the 'verse built for Stargazing, this is a world I would like to see more of. The OCs are interesting without being cloying, and that will always be a happy thing.
Broadcast Signal by ??? - Longish, plotty fic will always be my favorite. This is also Rodney-centric, and he's doing the best he can under really ugly circumstances. There's a bit of angst and hurt without real comfort, but the payoff at the end is well worth the journey.
The Bumblebee Myth by ??? - This is the crackiest crack!fic I've ever seen, and I absolutely love it. Rodney's a mantis, John's a stick insect (like we didn't see that coming), and -- yeah. Crack all the way.