Crumpets Aren't My Style by Marz1
General O'Neill is sent on a nice relaxing dipolmatic mission in the U.K. Of course, there's bound to be trouble when he runs into a murderous cult called the Death Eaters, whom appear to have somehow gotten their hands on alien technology.

Jack O'Neill and the Curse of the Salamander by Danielle Ducrest (Flatlander, Jr)
Jack O'Neill left the wizarding world in 1963 without any intention of ever returning. Loki's experiments change everything. It all begins when Jack's clone receives a letter from Dumbledore asking for his help. The favor? Infiltrate Slytherin. The problem? Jack wasn't a Slytherin the first time he attended Hogwarts, & once a Gryffindor, always a Gryffindor. Throw in Death Eaters, kidnappings, imprisonment, prophecies, & salamanders, & both Jack & his clone will wish they'd stayed in Colorado...

Magic Inside Me by Aussie-mel
An eleven year old Daniel discovers a whole new world full of magic and mystery when he receives a letter by mysterious means.

Nothing So Unusual by Alynna Lis Eachann
Sam, Jack and their kids have traveled the galaxy and seen it all. Or so they think. It starts with a letter...

Place Where I Belong, A by Corwalch
Voldemort has been defeated and Harry Potter has decided to leave the Wizarding world for good.

Portals and People by Danielle Ducrest (Flatlander, Jr)
Who the heck is that guy with the glowing green eyes?

Pottering Around by Conspiracy
A magical secret from Sam's past comes back to haunt her.

Unexpected Reunion by Big Hearted Angel and Jedi Bant
Daniel Jackson always new he was adopted but his past suddenly comes back to find him.

W Company, SG by Ryan
Hermione as an accident after book 4, and ends up at SG command four years in the past with no way back to her time. Willow left Sunnydale after Tara left her and joined airforce.

What If by Jedi-Bant
What if Qui-Gon had lived to train Anakin, but he still turned? What if Obi-Wan took a different Padawan after being knighted? What if Padmé was sent to Earth for her own protection? What if she was sent to Hogwarts to live? What if years later Luke, Leia and their families came to Earth to find her? What if Jack was a wizard? What would happen? SW/HP/SG crossover.