Shoot me not if this has been suggested earlier (I suppose it may have been).
Anyhow, I loved being a Lumberjack in a previous event. Why? I got to chat with people I normally would not have talked to. So my suggestion is:
Alliance chat channel in Torn chat.
I assume it would have to be maintained by a faction leader inviting other factions to join.
Edit: I know about Discord but that is not owned by Torn.com.