Mailing lists
Now we come again to a classic media: electronic mailing lists. They are both used for announcements and for discussion. If you subscribe to such a list, you will receive announcements and discussion contributions by other subscribers. You could silently receive and read all the messages, and you could send e-mails to the list address which would then be sent to all other subscribers. Now you know you should read an FAQ before.
Today many people prefer easier accessible media, such as web forums. However, these lists still exist and might be as long as e-mail is popular.
texhax
http://tug.org/mailman/listinfo/texhax
This is a list for general TeX discussion, a companion to comp.text.tex, established in the 1980s. It has hundreds of subscribers and there are many experts among them.
tex-live
http://tug.org/mailman/listinfo/tex-live
The name says it all: it deals with the TeX Live collection. If you installed this software distribution, you might be interested in subscribing to get...