In a french multi-fandom community I'm part of on LJ, we host a fanish Avent calendar: people register on the calendar post with masked comments indicating the day they want + what subject they want to talk about (fandom primers, squee posts, discussion on tropes or fandom trends, yearly recap, expectations for next year, etc), the mod put them on the calendar (without the subject to keep it a surprise), and of we go.
It's actually almost the only activity the community get anymore, but for now it's still come back to life every december. ^^