Basically, I will be excited by anything you write. I'm not a difficult person to please. I like my fanfiction in gen, het or slash varieties; it can be clean as a whistle or as smutty as you wanna get. I'm fond of humor, family affection, romance based on friendship, wacky adventures, sex in unexpected places, good-natured competition and even the occasional inevitable heartbreak. The only things I would ask you to avoid are humiliation and cruelty. I don't dig them, even in fanfiction.
Also, if you want to have a look at a fandom you don't recognize, the three movies are all on DVD and accessible through Netflix. Bujold's book series is more involved, though worth the effort, imho. The books featuring Miles and Duv interacting the most are Brothers in Arms, Memory, and A Civil Campaign. The Vorkosigan saga wikipedia page does a good line in synopses and suggested reading order.
Fandom-specific guidelines, in case you want them:
Danny Deckchair (Danny/Glenda)
I would love to see backstory for Danny, Glenda or both. What made them into the people we saw in the movie?
If I were forced to watch only romantic comedies for the rest of my life, this one would be in the DVD player 90% of the time. I love how these two characters bump into each other out of the blue (literally), but they turn out to be just what the other one needs and didn't even know they were missing. I think it would be cool to explore how Danny ended up drifting through life, or why Glenda won't let anyone in.
Lois McMaster Bujold - Vorkosigan series (Miles/Duv)
I'd like something focusing on the relationship between Miles and Duv. Slash would rock my world (set prior to their respective marriages), but friendship fic would also be very welcome.
Bujold's Vorkosiverse got me back into reading science fiction after a very long time away. I got tired of the sterility and technobabble so prevalent in a lot of the most acclaimed novels. With Bujold, you get the tech, and the worldbuilding, and the awesomeness of great interpersonal relationships. I love when Duv and Miles interact because Duv is so competely different from Miles, but he serves as a worthy foil rather than a 2D adversary. He has this great background all his own that informs his actions and reactions.
Real Genius (Mitch/Jordan/Chris)
What are Mitch, Jordan and Chris up to in the 21st century? Bonus points if they're all still friends or more.
One of my favorite movies of all time! What I love about this film and these characters is the idea that nerds have complicated inner lives, too. That and Val Kilmer being as outrageous as possible. =) I really would love any kind of glimpse into the future of these great characters now that they might have laptops and iPhones, plus jobs and all that adult baggage. P.S- They really hit my threesome kink, so while it's certainly not required, it would definitely be welcome if that's your thing as well.
Waitress (any)
I adore this movie, especially the ending, and I would adore future fic of any sort.
Honestly, I went to see this movie because of Nathan Fillion. And he was excellent, but so was everyone else. I enjoy the way the movie explores the different packages in which you find love. Jenna and Jim, Jenna and Lulu, Dawn and Ogie, Becky and Cal and Old Joe and the whole diner crew- you feel like you could wander in and have a piece of pie with them. I'd love to take a peek into the future of those relationships.
I hope this is helpful, most excellent Yuletide author, and not too scary.