I think of it as one.
AARP
The Sierra Club
The Rails To Trails Conservancy
The National Rifle Association
The Republican Party of Ross County (Ohio)
The Chillicothe and Ross County Public Library
Sam’s Club
I am a member of the Gesneriad Society.
And once upon a time I belonged to the North American Fruit Explorers.
I just hope Fred Phelps doesn’t hear about it. 
The Croquet Association
The AA (that’s the British version of the AAA - I’m not an alcoholic - yet :))
The University of Nottingham Gilbert & Sullivan Society (G&S for short)
Various other student groups and clubs.
I guess the SDMB is kind of a given for anyone replying to this :).