Venite Adoremus!
A Catholic forum. Join or start a discussion of current issues in the Church.
http://www.ok13.com/discus/messages/201/201.html

Catholic Corner
All Catholic moderated Java chat environment, faithful to the Holy Father. Also a message board for Catholics and those wishing to learn more about the Catholic Faith, with various forums and topics.
http://catholic-corner.com/

The Catholic Message Board
A relatively censure-free web-based discussion forum, so long as you are polite. Anyone can read; registration is required to post.
http://forums.catholic-convert.com/

Beliefnet Discussions: Catholicism
More than a dozen discussion boards. Topics include Church teaching, sacraments and the Mass, the papacy, and women in Catholicism.
http://www.beliefnet.com/boards/boards_main.AllCategories.asp?Category=58

Faith Chat
Low-traffic retromoderated web-based discussions about the Catholic faith. Also offers free POP e-mail accounts.
http://faithchat.org/

Catholic Young Adults Online
A message board for young adult Catholics who follow the Catholic Church on all issues, social, political, sexual, and spiritual.
http://p216.ezboard.com/bcatholicyoungadults

Catholic Pillar & Foundation
Message board with general discussion of Catholic topics. Also news items, apologetics. Anyone can read; posting requires free registration.
http://p075.ezboard.com/bcatholicpillarandfoundation

Catholic Discussion
Canadian Catholic site message boards. A personal initiative. Does not tolerate dissent.
http://p078.ezboard.com/bcatholicdiscussion

Once Catholic
Message boards for Catholics who have left the Church and are considering a return. Moderated. No registration required.
http://www.oncecatholic.org/