Both the UPP, which Carl mentioned, and the PPC to which I now belong circulate folios of pictures around a small group of members, typically 10 to 15. It the case of the PPC we make 5" x 7" prints to circulate, enjoy and comment on. Apart from the enjoyment, and challenge of producing small pictures, it puts a little pressure on me to get out snapping occassionally. I have never though of the term "Circle" but it must derive from circulate as you suggest. Our website is worth a look, lots of information there.