Newsgroups

How do these work?
How do I sign-up and recieve(?) from a newsgroup?

You mean usenet groups?
[list=1]
Select a newgroup server (usually provided by your ISP)
Select a newsgroup;
subscribe to it.
[/list=1]
This is all done using your favorite mail program, which should support this.
If you don't have access to a mail program or don't wish to use it, you can always try google groups (http://groups.google.com/); worked fine for me until i got bored with visiting them.