torch_wood is a general Torchwood community.
torchwooduk is "currently under construction".
torchwood_three is another daily newsletter.
tw_declassified is a discussion community.
torchwood_aus is for Australian fans.
tw_archives is for general and less explicit Torchwood fan fiction.
jack_in_cuffs is for darker or more explicit Torchwood fan fiction.
torchwood_fic is an anything-goes fan fiction community.
tw_exchange is a fanfiction exchange community (first challenge is Christmas 2006, see info for details).
tw_wotd_fic is a community with daily prompts.
tw100 is for drabbles.
tw_flashfic is a flash fiction challenge community.
torchwoodicons is for Torchwood icons.
torchwood_chllg has icon challenges.
torchwood_100 is a challenge community for making a set of 100 icons.
torchwood_files is for Torchwood fan videos.
galactic_conman is for fans of Jack Harkness.
torchwoodcoffee is for fans of Ianto Jones.
owenharper_fans is for fans of Owen Harper.
pcgwencooper is for fans of Gwen Cooper.
outside_bf is for fans of Rhys.
suzie_costello is for fans of Suzie Costello.
toshiko_sato is for fans of Toshiko Sato.
There are also communities dedicated to some of the actors who've appeared in the series,
including John Barrowman, and one for writer Russell T. Davies.
absolutly_brill is a Jack/Gwen community.
3handedjack is a Jack/hand community.
gimme_the_jar is also a Jack/hand community.
ratjamandpizza is a Gwen/Owen community.
gwentoshiko is a Gwen/Tosh community.
at_the_ritz is a Jack/Jack community.
jack_and_gwen is also a Jack/Gwne community.
jackxianto is a Jack/Ianto community.
jashiko_tw3 is a Jack/Tosh community.
toshianto is a Tosh/Ianto community.
torchwoodslash is a general slash community (fanfiction, fanart, discussion, icons, etc.).
tw_femslash is a general femslash community.
tw_transcripts is a Torchwood transcripts community.
torchwoodquotes is a quotation community (anyone can post).
The official BBC website.
Torchwood.org.uk (a.k.a. "Torchwood external hub interface.")
The newbieguide to Doctor Who fandom on LJ is
Please comment in the case of any broken links or deleted/inactive communities.
Last updated: 08/05/07.
Thanks to spiralsheep for getting this started.