Popular sites accessible normally through your E-Mail program to which you may have access, usually by free subscription, and thousands of these exist for specific interest groups.

Discussion groups with common themes on USENET.

Discussion groups built around a particular topic. Some are managed, others are not. Usenets take two forms: email groups, where subscribers receive comments and postings from other users, or bulletin boards, which users access to read posted messages or to post their own.

are electronic bulletin boards where messages can be posted (similar to an e-mail) and then read and replied to by anyone who subscribes to the News Group (subscription costs nothing). There are thousands covering all sorts of interests, many eccentric.