The Compulink Information eXchange is a UK-based, commercial conferencing system or BulletinBoardSystem. It was established in 1984. Nowadays it has turned itself into an ISP but the conferencing side is still thriving. A subscription costs around £10/month.
It currently has around 7000 conferences. I think it is remarkable that a fairly large community could have survived so long without succumbing to the signal-to-noise ratio problems that seem to beset Usenet, SlashDot and now Ward's Wiki.
I've been a member of CiX? for some years now. I think the key to its success has been the sense of community it has managed to generate. Also as, in theory, all conferences are moderated there are checks on some of the more blatant abuses. With regard to signal-to-noise it's a case of one man's meat in many of the conferences. There can be some blisteringly hot flamewars and a huge amount of wibble. However, if you don't like it you can resign a topic or a whole conference. One of my favourite things is that its database is persistent i.e. all posts, apart from those lost in the great crash of 19.., can be accessed. I still recommend it as a source of good, free, technical support. --DaveMorgan?