Actually, I had this idea a while ago, during the Revengefic heyday.  
Seeing all the creative activity the "Revengefic Challenge" caused, I 
wondered if people could use other "challenges" to get the ink flowing in 
their veins.  Not specific fanfic "ideas" but writing exercises that 
might get people out of a rut if they're stuck there; I have a book that 
has some ideas that could be adapted specifically to fanfic writing, and 
others that might be useful to try in a fanfic genre, plus a few of my own.

If anybody's interested, let me know, and I'll post the first one.

mata ne,
bengman

bengman           *"Nanika kuwasero, tonikaku kuwasero, zenbu kuwasero! 
Bridget E. Engman * Demae mo ii ze! Henshin shichau to yubi ga futosugite,
b-engma@students. * Pizza no chuumon sae mo denwa dekinai!"
   uiuc.edu       *   ---Wan Dabada, "Can't Stop Eatin'"