I think I'm going to try NaNoFiMo again. (I first signed up in 2005.) Maybe this year, I'll actually get somewhere. Some possibilities:
Grayed - started around 2002-2003, science fiction/suspense. An investigator searches for answers as the death count of an icy mining colony rises.
Salamander Hill - unofficial 2004 July Nano, fantasy western. A band of adventurers search for treasure in a fabled place called Salamander Hill.
On Vacation - 2006 3-day novel, modern fantasy. The Eater of the Dead takes a cruise ship vacation--except it might turn out not to be a vacation at all.
Baliser - 2006 NaNoPubYe warm-up, biopunk. The night janitor inadvertently stumbles onto a plot to kill people who are carriers of a very unusual disease.
Greenglass - 2007 3-day novel, historical fantasy/steampunk. A prequel to this year's Nano Vellum and Green Vitriol
Right now, I'm leaning towards doing Baliser because I have most of the world building done up and it relies heavily on my expertise (microbiology). I'm also quite fond of the main character who is a down-on-her-luck cleaning lady.