The 12-Step Recovery Meeting Hall in Second Life has been around since at least 2008. It's a location in Second Life founded by SL avatar Spike Willard, and is used to host scheduled meetings for participants of 12-step recovery programs.
The meeting hall used to have regular meetings every week. However, it seems that activity in the group has been lower lately, and you must now specifically request for a scheduled meeting to be held. Due to this I have been unable to experience a meeting first-hand, but I think a lot of what goes on at a meeting can be inferred from the environment that the meetings take place in.
The meeting hall consists of a small cabin-like structure with a large table and some chairs inside. There are some posters displaying information about 12-step recovery programs. Presumably everyone sits around the table and discusses their experiences with addiction recovery, much like a real 12-step recovery meeting.