I haven’t had much luck finding other Quakers in SL. When I search on “Religious Society of Friends” I don’t get anything. “Friends”, of course, gets all sorts of things that aren’t related to Quakers. And then “Quaker” does get a few hits. There’s a group (that doesn’t seem to have a way of admitting new members, and which is very small) called Quaker’s sword, but I’m not sure they’re really about being Friends.
In doing a Google search, I found two SL bloggers who mention belonging to a Quaker meeting: Rik Riel and Caliandris Pendragon. I haven’t looked them up yet.
I’ve been wondering about converting my Rockridge model house into a meetinghouse. I already removed the kitchen, so there’s a large room in the back that would be nice for a meeting room. I’d just need to make benches and get pose balls and animations for sitting in worship. Being uninvolved with Friends right now in RL, it seems a little weird to be thinking about, in effect, creating the setting for a worship group in SL, but I do keep being drawn to the idea.