Flying Lessons by VR Trakowski is a sweet little Simon/Kaylee vignette that does a lovely job with both characters, and is full of nifty little details and insights.
Mood to Burn Bridges by Sarahetc is so far my favourite of the "How did Mal take Wash and Zoe's relationship?" stories, in part because all three characters just come across exactly how I would picture each of them in the situation. Love Sarah's Wash , in particular.
It Was Night by
Pyrrha Cottonwood is the Objects in Space coda I wish I had written, full of subtlety and light touches, and excellent characerisation of Simon, Kaylee, and Mal.