A usenet group, also known as a newsgroup, is a collection of usenet articles. It is different from a web site, a mailing list, a bulletin board, and most other constructs.
Usenet groups can be public (meaning that they may be accessed via many servers) or private (meaning that the articles are accessed via a small number of servers - perhaps one). Some private newsgroups are protected so that one needs a password. Even though a newsgroup may be public, that does not guarantee access to it via any particular news server or archive though - each usenet provider has the freedom to pick and choose what newsgroups they provide. A URL for a public newsgroup follows the form 'news followed by a colon followed by the newsgroup name (which generally follows the form of a tree hierarchy separated by periods).
Some public newsgroups relating to Tcl are:
LV Note that http://groups.google.com/ provides a WWW based interface to posting to a variety of newsgroups. The process requires you to obtain a verified login to google, and the turn around for reading posts is slow, but it does provide an alternative for those who have difficulties accessing the groups via nntp.
Feel free to list other newsgroups which cover tcl to some degree.