The Mackelroy Chronicles. Book One, Galahad's Overture, is complete. Book Two, Ellen's Song, is in progress and mostly complete - sixteen of an estimated twenty-six chapters. I've got solid ideas in place for Books Three through Seven, plus rough notes for possibly another two. And the series is open-ended; I have no idea how far it might go.
A prequel of sorts has also been on my mind, The Adventures of Thomassin and the Lady Matthilde. This one will cover, among other things, how Jake and Marga met.
My NaNoWriMo novel, Harry Potter and the Water-Born Blade, and its planned sequel, Harry Potter and the Orb of Winter's Breath. Both of these are going to be full-length novels, covering Harry's sixth and seventh years at Hogwarts. They are consistant with canon through JKR's Book Five.
I have an adult-oriented furry one-shot, also novel-length, in the works. It's set in the same world as the Mackelroy Chronicles, and there will be some minor character crossover, though it's actually stand-alone.
I've got a fanfic in the works for the Hiyao Miyazaki film, Kiki's Delivery Service. It starts shortly after the film ends, and continues through the end of her journeyman year and beyond. How far beyond, I'm not certain - there are scenes sketched in which would likely take place some years later, when Kiki is at least nineteen.
I was thinking earlier this week, and an incident which will be coming up shortly in Water-Born Blade spun off and attracted my attention. Should I do this (and it seems likely, the way it's taken root), it will wind up being a crossover story between my Harry Potter stories and my Kiki fanfic. It would likely be set around the year 2000.
Geez. That's fifteen novel-length stories in progress - and these are just the derivitive works. I've got enough to keep going for years at this rate.