While I don't write many Atlantis fics, most of the ones I have done have been for the weekly Stargate writing challenge LiveJournal community, sg_challenges. Most of the fics I have done for this community are for SG-1, and can be found here.

Synchronized
Special Challenge #5 - Canada Day: A Canadian, Oh Canada!
Rating: PG
Genre: Humor
Spoilers: None
Summary: McKay and Sheppard discuss Earth holidays.

I Said Don't Touch Anything
Challenge #20: "I know you are, but what am I?", a jerk
Rating: PG
Genre: Humor/Drabble
Spoilers: General season two spoilers
Summary: Sheppard touches something and acts his age. McKay is dragged along for the ride.

Brilliance Doesn't Come Easy
Challenge #21: Numbers, Calculations
Rating: G
Genre: General/Drabble
Spoilers: None
Summary: McKay complains about impossibility.

On Purpose
Challenge #26: Walking, Feet
Rating: PG
Genre: General/Drabble
Spoilers: Sateda, Phantoms
Summary: Rodney complains. (So what else is new?)

Sinking
Challenge #33: Night, Day
Rating: PG
Genre: Suspense/Drabble
Spoilers: Grace Under Pressure
Summary: Hanging on by a thread.