Great to see this thread here. I helped start a 70-voice non-audition choir that sings folk music from around the world. It's called "Common Thread: Community Chorus of Toronto," and it just celebrated its 10th anniversary in June.

After about five years of really hard work in organizing and running the choir (singing in the alto section the whole time), I backed off and became a regular member for a few years. Now I'm not even a member anymore, because my teaching schedule has just been too crazy. But I still keep a hand in with a few things here and there.

http://www.commonthreadchorus.ca/

Folks might also be interested in the Ubuntu Choirs Network, which is a network of community choirs, mostly based in British Columbia:

http://www.ubuntuchoirs.net/

The people who started the Ubuntu choir network also run a Community Choir Leadership Training, which looks amazing:

http://www.communitychoirleadership.com/the_program.php