fic-finding?

There's a lot of places online where one can go to find the title and author of a book when all you remember is that it had a cool scene with pirates juggling coconuts -- oh, and the cover was blue with silver metallic trim.

Anyone know of someplace that does the same thing for fanfic?

(This post brought to you by my finally reading Guards, Guards!, resulting in the wish to find a series of really sweet Vimes/Vetinari fics that I read several years back.)