Vatican2(site info)
A mailing list for discussions of how the Church might more fully embrace the reforms of Vatican II. The focus is scholarly and issues oriented. Sponsored by ARCC, for progressive Catholics.
http://astro.temple.edu/~arcc/vatican2.htm
2.
CIN Mailing Lists(site info)
Dozens of email discussion groups on all kinds of topics: CIN Main for general Catholic discussion. Some lists more active than others. This is a good source although moderation is sometimes uneven on some of the lists.
http://www.cin.org/mailman/listinfo/