Just a couple of quick tips and things to point out after spending a few minutes chatting with everyone in the group.

At this time you either can't (or it's not apparent how to) opt out of chat for a given group. You have to sign out of chat all-together.

You can opt out of email notifcations by clicking the "Edit Notifcations" on the top right of the Group window.

If you comment on a post, you're automatically subscribed to that post and begin recieving notifcations when others comment. You can also opt out of these on a per-post basis by clicking the "unsubscribe" link under the title of each post.

Hope that helps alleviate some of the noise so the group stays useful to everyone.