Recurring Nightmares and A Time To Heal by Shanna continue the Simon saga begun with Cat and Mouse Games, and together are a gripping action story grounded in the characters and their relationships, with spot-on characterisation for everybody, and a lovely bit of Simon and Kaylee interaction which takes into consideration all the roadblocks a potential relationship between the two would have to conquer first. Also, there's Cat. Cat makes everything better.
Left Behind by Ana explores one AU for each of the characters, and how the entire crew would deal with dire consequences and how the dynamics might shift. Not exactly cheerful, but definitely a fascinating look into the group dynamics.
Where I Cannot Stand by Hawkmoth is a lovely little gem set mainly during the war. We can blame Sharpe on tape for this one, and I for one say bring on the Sean bean marathon, if it always yields fic of this calibre.
Cat and Mouse by Bookworm is a nifty keen story set post-"Objects In Space" which does an excellent job of creating believable tension, and exploring Mal in particular.
Along The Way by Trisana McGraw is a lovely little Simon/Kaylee snippet which just brings me all sorts of joy. If you're looking for something to just make you grin like a fool for a few hours, this is the story for you.
Of Battles and Bandits by Nicole Clevenger once again displays Nicole's uncanny knack of knowing exactly Zoe would say, and how she would say it--and captures the Mal/Zoe relationship perfectly. I also love her continuing subplot of Mal trying to wrestle with how he feels—or doesn't feel—about his first mate. Lovely, subtle, true to all the characters, and it even is kinda plotty. Complications picks up where Of Battles leaves off to a degree, and is one of the very few Mal/Zoe stories that feels completely believable to me. Even Wash/Zoe fans I think will find it spot-on.
At Ends by northlight is a beautifully structured look at war, and Zoe, from three angles. I can't describe it; I can just tell you you should read it. Preferably twice, and right away.
Lost'n Found by Igeria is a very brief (it was written for a Firefly Friday challenge) but incredibly effective look at Simon and Mal. The dialogue is just right on the nose, and it's subtle and tasty, and hints at a lot more than it shows at first glance. Also, it has dinosaurs.
The Other Side of Serenity by Archer is just a nifty keen look at how the Battle of Serenity might look to someone on the "right" side.
Like A Stream by Maystone shows the darker side of the Firefly 'verse, when Mal and Jayne take off looking for a missing River.
Sturdy by Ana takes a minor character in one of the as-yet unaired episodes, and spins a gorgeous yarn that captures the flavour of the Firefly 'verse just perfectly. Elegant, subtle, and truthful to the core, it will give you a whole new perspective on Heart of Gold.