MimerDesk is a Web-based groupware environment designed for a wide variety of uses such as personal management, computer-supported collaborative learning, carrying out projects, and setting up communities.
How about these features (kind of like Facebook):
o read messages online if they prefer not getting Email
o post messages to the group from the web Email tool
o personal TODO list, calendar, address book, files, friends
o group email, files, links, address book, reviews, calendar, news,
voting, projects, and forums (chat is not working for now)
o Easy visibility of all group members, with only the details YOU want
to share with others visible.