It doesn't matter if the stories are brand-spakin' new, or if you want to post older, completed stories. Just post your story to the community or your link to the story between now and October 31. On the big night itself, there'll be a master list of creepy stories for everyone to check out.
Naturally, I sent The Missing Bits over to the community (which was posted here in June 2006) for inclusion into the master list.
Right now, I appear to be a Halloween entry of one. Please contribute so I don't feel so lonely.
If you don't, I'll make sad-face at you until you do.