Chats_and_Forums

See also:

The Coconut Internet - A theories and games message board.
Coffeerooms: Lost - General show and episode discussion.
The DarkUFO Forum - Show, cast, character, episode, and theory discussion.
DharmaSecrets - Show, cast, character and theories discussion.
Let's Get Lost - A weblog about Lost news, spoilers and updates, as well as recaps of all the episodes.
Lost Community UK - Cast, character, episode, and theory discussion for UK fans.
Lost Discussion Board - Forum dedicated to the discussion of Lost.
Lost Exposed - Clues, news, forums, blogs, and spoilers
Lost Forum - Discussion of episodes, characters, and relationships.
Lost Message Board - General show discussion.
Lost News and Images - LiveJournal community.
Lost Paradise - Discussion of characters, episodes, and spoilers.
Lost: The Show - LiveJournal community.
Lost TV Forums - Discussions on episodes, spoilers, theories, and it has a list of character forums. It also offers complete transcripts from every episode to date, as well as fan fiction and fan art posting boards.
LostTalk.net - Discussion forums on the show, episodes, characters and theories.