Mainly straight-up adventure and some drama. I've also tossed in a few romantic Chalion fics at the bottom.
Aptitude by Philomytha
A young Miles adventure, in which he unmasks a double-agent... but nothing's quite what he thinks. Ivan is involved (of course) and there's really excellent Illyan as a bonus. KikiRec
By No Miracle or Majestic Means by Riko
Ivan foils a terrorist plot. Well, sort of.
Chargee d'affaires by Magglenagall
Ekaterin races desperately for Cetagandan space, with a dying husband in tow and the wieght of empires on her shoulders. Really excellent Ekaterin POV, filling in the holes when Miles was out of it. KikiRec
The Emperor's Garden by hedda62
Barrayar's future, in flowers. a beautiful story built around Ekaterin redesigning the Palace gardens, with multiple beautiful POVs. KikiRec
Five Ways Ekaterin Never Met Miles at Twenty by sahiya
Five perfectly plausible scenarios alternating between giddy and heartbreaking. KikiRec
Guerrilla by Glishara
A quite dark AU -- after a very important message fails to get through, Cetaganda invades, and the only Vorkosigan left to meet them is Ivan. Unflinching and suspenseful, and Ivan in particular is written beautifully. Character death all over the place, though.
The Hand That Rocks the Cradle by Philomytha
Another excellent missing story; Alys's flight through the streets with the newborn baby Ivan and Koudelka. This could be written by Bujold; the voices, descriptions and details ring absolutely true.
Intimations of Maturity by Kassia
Simple but sweet--Ivan and Miles on a double-date, back in the days before the Dendarii. Ivan's voice is just right, giving us a nice view of his relationship with his cousin, and the depth of character that he'll eventually develop.
Lilies of the Field by Raven (singlecrow)
"Cordelia," he interrupted, "I presume that at some point you're going to explain how you came to be reading Gregor's prospective mother-in-law's doctoral thesis?" Cordelia and Alys, doing women's work.
A Maze of Twisty Passages, All Alike by Merry
At last, someone gives Ivan the story he deserves! A marvelous adventure; Ivan rescues Gregor from a dungeon (sort of), but has no idea how to finish the job and actually escape. I adore Ivan and this story works wonderfully for him.
The Mirror Dance series by josan
A gorgeous, gorgeous series of short stories immediately following the action of Mirror Dance, set largely during the recovery of all injured parties at ImpMil. Josan's take on each character is heartwarming and heartbreaking -- Cordelia's voice in particular shines perfectly, but Aral and Mark's interaction is also a thing of beauty. I've linked to the applicable LiveJournal memories; start with "Night Visit" and read through "The Winterfair Ball".
Mission Reports by Gwynne
"Illyan (beta-reads Miles's fanfic) edits Lieutenant Vorkosigan's reports." Short, very funny.
The Morning Coffee by Glishara
"Emperor Gregor confronts a harsh truth about his foster-brother Miles, and he and Simon Illyan must debate the course to follow." Precisely how a certain very ugly conversation must have gone. KikiRec
Saint Miles dy Vorkosigan by tuval
"Miles, aged fifty, discovers a portal into Chalion and rides off to save Mark with the Bastard's aid." Aligns Bujold's two world with a deft touch and a good story.
Shelter and Solace by Dira Sudis
"We will go to Beta Colony. I have some family there, I think, and--a friend." Sad but hopeful au for Aral, Gregor and Cordelia. KikiRec
Uncle Simon by Philomytha
"Simon has no children of his own. But he has an honorary nephew." Simon's relationship with Miles over the years. KikiRec
Venture Capital by altariel1
Mark cuts a deal with an unexpected business partner. A great little post-A Civil Campaign story that shines a spotlight on Laisa as a human rather than an Empress.
Worst Things by Gwynne
"What's the Worst Thing that could happen? A game that anyone can play." Awesome, spare and perfect look at the third generation of Vorkosigans and Vorbarras. KikiRec
A Chalion Romance by mrstater
Awwww... Lovely bits of Betriz and Caz's courtship and marriage.
Communion of Saints by rthstewart
When it is dark enough, you can see the stars. ~Ralph Waldo Emerson
Saints can find communion but may have to crawl over rough ground to get there.