DNews 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
Leafnode a Usenet system for small sites running any flavor of Unix, with a few tens of readers and only a slow connection to the Internet.
http://www.leafnode.org/
Netscape Collabra Server Users can create discussion groups, track discussions across multiple groups, and monitor discussions for content. Operates over SSL for security. Handles HTML and other media formats. Offers moderation features. For Unix or Windows NT.
http://home.netscape.com/collabra/
NewsCache 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/
Newscaster Beta implementation of Usenet news via multicast for Solaris and Linux. Other platforms may be added upon request. Author seeks feedback on the program.
http://www.newscaster.org/
Newsplex Personal server utility which allows any news-reader to access several news-servers simultaneously, by merging their content into one single news-server. Linux and Windows versions.
http://triceron.com/project/newsplex/
NNTPCache Pretends to be an NNRP news reading server. Passes NNTP commands to news-servers, takes output and caches and indexes it. Creates a large "virtual" newsfeed, without the bandwidth or drive space normally required. Freely available. Compiles
http://www.nntpcache.org/
NNTPRelay 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/
sn 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/
SuckMT Uses client NNTP to download news messages in order to feed them into your local server. Free download, FAQ, sample scripts, planned features. [Linux, Windows NT, source/binary]
http://www.wirehub.nl/~basjesn/suckmt/