Netropolitan :

MANY more services are available to e-mail users than simply sending
messages
to friends and colleagues. Users can join mailing lists and discuss
thousands of
different specialist topics with like-minded people around the world. You can
see whether there is a mailing list which covers your favourite topic by
sending
a blank message to liszter@bluemarble.net or, if you or a friend
have Web
access, you can go to http://www.liszt.com/.