Fictional Fans

I've got more, but a handful of fandom-specific ones for now:

Doctor Who

who_allsorts (A mini-prompt table challenge for DW.)
who_guestfest (annual DW Minor Characters ficathon, now underway)
doctorwho - general comm for the fandom
dwfiction - for DW-related creative endeavours
who_at_50 - another general comm

Blake's 7
blakes7 - general comm
b7friday - fortnightly flashfic comm (new prompts every other Friday)

Also: sapphire_and_steel - general comm.