Usenet is a worldwide information network made up of user-generated discussion groups called newsgroups. There are over 110,000 Usenet newsgroups, which cover a vast variety of subjects ranging from space science and exploration to Apple iPhone app development and technology. Usenet is the oldest community on the internet and all content found on Usenet is user generated, just like forums and blogs. In fact, Usenet is the forefather of these thread-based systems.
Usenet is made up of a network of servers all over the world that sends and receives messages or posts from millions of end-users engaging in new and ongoing discussions. Originally designed as a way for colleges and Universities to share news, ideas, and information, the growth of the internet has given way to an explosive flow of information on the Usenet, making it an international breeding ground for individual and group creativity.
In addition to the discussion-based nature of text newsgroups, there is also an abundant amount of Usenet newsgroups and messages that contain user-generated encoded binaries. These encoded binaries can be any type of file ranging from MPEG video to MP3 music files.
Here are some links with a LOT of good information: