Specify a fandom or a pairing if you like, or if you have no preference that's fine too!
Posting fic in response to other people's responses is always excellent, as is posting fic with no prompt at all.
I think the spirit of this is closer to writing shorter fills and just stretching those creative and imagination muscles, but if something really grabs you and you want to write a mini-novel then go for it!
Closing date is probably going to be when Winter arrives to rudely shove autumn out the door.
Naturally everyone and anyone is welcome to participate.