A Traditional Catholic Mailing List 
Lively discussions between Traditional Catholics, Protestants, and other faiths. Most participants are from FidoNet's R_Catholic discussion group.
http://rcatholic-l.freeservers.com/Vatican2
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
CIN Mailing Lists
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/MailLists.html
SISTER-L Mailing List
International electronic discussion group focusing on the history and contemporary concerns of women religious (sisters and nuns). Founded in July 1994, it now has about 900 subscribers throughout the world.
http://www.maxwell.syr.edu/maxpages/faculty/msthomps/aboutsl.htm
