Complete Usenet system. De-facto standard for handling news routing, news spool and serving the spool to customers. Free. Available for various versions of Unix from the Internet Software Consortium. How-To's and mailing lists. http://www.isc.org/products/INN/
Usenet NNTP news server for most flavours of Unix, as well as Win9x/NT. Handles full newsfeeds while conserving system resources. Can use Suck feed option. Anti-spam features. Academic licensing also available. http://www.netwinsite.com/dnews.htm
A small news system for sites with a slow connection to the Internet that serve, perhaps, a few dozen newsgroups. Also includes a mail-to-news filter. For Unix-type systems. http://www.iki.fi/patrik/sn/
The only carrier-class news router for Windows NT. Freely available. Also available from the same authors is the freely available news server program "Tortoise" for Windows NT. http://nntprelay.maxwell.syr.edu/
Usenet News cache server for Unix. Distributed under the GNU Public lisence. Reduces required network bandwidth of the news server. Multiplexes between different news servers and allows offline news reading. http://www.infosys.tuwien.ac.at/NewsCache/
Offering several products for discussion software: Cyclone News Router, Typhoon News Server and Twister Discussion Server. All products run on a Unix/Linux/Solaris type of operating system. http://www.highwinds-software.com/