A large part of the reason for this site to put people in contact with other people. Digitally there are quite a few different ways.
Chat rooms.
Instant messaging.
Email
Bulletin Board - easy to manage
SMS on your mobile - some phones do instant messaging as well.
The idea is to offer several forums for the exchange of information, for discussion and just plain blah blah blah.

I haven't set up any of this stuff on a group basis so have no idea what is involved technically or what will work best.
Do you know of any good sites or services that you have had good experience with?
Do you know anything about security in these areas.

What else can you think of here ...?