schneefink

When I started looking for Vorkosigan fic I went to the AO3, sorted by kudos/bookmarks, and started from there. It worked very well, I found many great stories that way & I can recommend that method.
But just in case you want more specific recs, I also have a list! Part 1, here are some stories I enjoyed that deal directly with events of a novel.

Shards of Honor
Aral Vorkosigan's Dog by

Philomytha
gen, 76k
Summary: Illyan is assigned to watch Aral Vorkosigan during the Escobaran war. Soon he has to choose between his duty and his conscience, and the consequences rapidly get beyond him.
Why I loved it: I already recced this, but I'm including it here for completeness' sake. It still works very well now that I've read the book, and now I can fill in the blanks of what'll happen later, it's great as a prequel and additional PoV.

Warrior's Apprentice
Warrior's Apprentice: Scenes From the Other Side by

avanti_90
series, gen, 17.8k
Summary: What was happening on Barrayar while Miles was off playing with his mercenaries?
Why I loved it: oh, Gregor. And Aral. This is very well done, it shows how much the situation was hurting both of them.

Proof of Loyalty by

Chrys
gen, 15.6k
Summary: Miles returns to Barrayar at the end of The Warrior's Apprentice – one day after he is convicted of treason.
Why I loved it: It could have happened so easily! Some of the details of what happens seem a bit unlikely, but I don't care because it's so satisfying for my id. I might have read two specific scenes ten times.
It's part of a series, but part 3 and 4 deal with a different topic (Ivan/By.)

The Vor Game
Black Ice by

Philomytha
gen, 2.6k
Summary: Count Vorhalas receives an unusual visitor late at night, with an even more unusual proposal. Set during The Vor Game.
Why I loved it: Politics! I love politics, and these two work great together here.

Responsibilities of Command by

gumbie_cat
gen, 2.2k
Summary: After the end of The Vor Game. Miles may have passed the Gregor problem up the chain of command, but his subordination problems are ongoing. He can't resist the urge to check on things before leaving on his galactic adventure.
Why I loved it: More Miles and Gregor after their adventure, excellent.

Borders of Infinity
Money often costs too much by

Elfwreck
gen, 2.4k
Summary: Miles' expense reports ranged from intriguing to astronomical; Illyan was prepared to have to justify his special ops budget eventually. The hard part would be convincing them to let him keep handling it his way. Timeline: Post-Borders of Infinity; pre-Mirror Dance.
Why I loved it: Accounting and politics, made more complicated by Miles: poor Simon. Absolutely hilarious.

Brothers in Arms
Down by the Sea by

james
gen, 1.7k
Summary: Ser Galen and Mark threw Ivan into the chamber, then closed the hatch. Galen called Miles to tell him just how long he had to save his cousin's life. Ivan, however, isn't privy to what is going on outside the chamber. Written for angst_bingo, square 'tight spaces.' Set during 'Brothers in Arms.'
Why I loved it: Great Ivan PoV.

Memory
The Morning Coffee by

Glishara
gen, 2.9k
Summary: Emperor Gregor confronts a harsh truth about his foster-brother Miles, and he and Simon Illyan must debate the course to follow. Written for the prompt, "Gregor and Simon's discussion about whether or not to kick Miles out of the military in Memory," for the bujold_fic ficathon 2010.
Why I loved it: This fic does a great job showing just how painful Miles' betrayal was for Simon and Gregor as they discuss what they will have to do.

Anamnesis by

linman
Alys/Simon, 31k
Summary: Simon used to be afraid of getting lost. A collection of missing scenes from the events of Memory.
Why I loved it: This is very well done, all of it: Simon, the relationship between Simon and Alys, the other missing scenes. One of those fics where I already anticipate that in a few weeks it'll be hard to remember which parts were canon and which not.

Captain Vorpatril's Alliance
Captain Vorpatril's Plotbunnies by

Bracketyjack
gen, 15.6k
Summary: Four scenes in the life of Emperor Gregor Vorbarra, prompted by lines from Captain Vorpatril's Alliance.
Why I loved it: Gregor's life is hard. Great missing scenes.