Here are some examples:

http://www.astraldynamics.com.au/forum.php
http://theholisticcare.com/forums/index.php
http://forums.riverofenlightenment.com/

Useful, because the people at all three would (likely) be willing to answer questions about things like keeping out spammers and keeping the discussions civil. Selecting a team of moderators and advertising for members and so on. That kind of thing.