My wife had the same idea, however, she's focusing on sub-cultures. For instance, people who get tattoos; people who play Warhammer; stamp collectors and so on. She's interested in what makes the very ardent ones tick.
In my mind, there's a line there. For clubs or organizations, what's below that line -- and what's above it? For instance, the military is a very unique, weird society with its own language, practices, traditions and so on. But, well accepted within society. Whereas a covention of hardcore Everquest gamers is lunacy. And UFO chasers?
Here are a few others that caught my eye, and these are only in Indiana:
Indiana Ghost Trackers
Mutual UFO Network for Northern Indiana
Kentuckiana Bigfoot Aerial Phenomena Research Organization
Independent Crop Circle Research Associates
Willard Library Ghost Chatters see their Ghostcam
PROOF Paranormal, Indianapolis
Southern Indiana Paranormal Investigators
ParaScience
Indiana Paranormal Investigations
SIGIL Paranormal
Unseenpress.com, Inc.
Indiana Paranormal Investigators Society (IPIS)
Northwest Indiana Shadowchasers
Rick Hayes and LifesGift Inc
I'm pretty sure I'd love to show up with a thermos of coffee and my notebook to any of these.
Then you get into splinter orgs like NAMBLA, MENSA, Thespians (I'm a member) and so on. So, it would seem the angle for the book is really on what a "normal" society sees as acceptible and what is not in terms of practices.
Of course, one of my favorite of all time:
The He-Man Woman-Hater Club, started by Alfalfa. That seems to have taken roots with men everywhere.
jt