EmailList-Managers - join
A help list for listowners and moderators using any service or software, Google Groups Beta, Yahoogroups, Smartgroups, Topica, Mailman, Majordomo, and more. The EmailList-Managers FAQ website: http://www.emaillist-managers.com/
Low activity, 734 members, restricted

Yahoogle - join
Yahoogle helps people understand their options when migrating to or from YahooGroups and GoogleGroups.
Low activity, 3655 members, moderated, restricted

Groups Test Group - join
Unofficial Google Groups test group. Group owner: Tomi Häsä.
Low activity, 306 members, restricted