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

Diablo
   Open source newsfeeding and newsreading software. Runs on most flavours of Unix.
   http://www.openusenet.org/

Extra Systems NNTP Server
   Freeware for Windows.
   http://www.esns.org.ua/ESNS_EN.HTM

Ftp.tin.org: Server Software Repository
   Hosts several Usenet server packages including Leafnode, C news, Diablo and INN, and also very old applications like A news and B news for historical purposes.
   ftp://ftp.tin.org/pub/news/servers/

Hamster Classic
   Light, open source NNTP and e-mail server. For Windows 95 and above, also runs under GNU/Linux with Wine.
   http://www.arcorhome.de/newshamster/tgl/

Hamster Playground
   Free newsserver and mailserver software for single computers and small family or company networks. Developed from the same source as Hamster Classic. Source available. [Windows]
   http://www.elbiah.de/hamster/

Hamster with news.individual.net
   Short tutorial with screenshots on the configuration and use of Hamster with individual.net news server. May also be helpful for other servers.
   http://news.individual.net/configuration/hamster2.php

Highwinds Software
   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/

How to Become a Usenet Site
   Periodic posting about the basic steps involved in configuring a machine to store USENET news.
   ftp://rtfm.mit.edu/pub/usenet-by-hierarchy/news/answers/usenet/site-setup

INN: The InterNetNews Package
   Complete open source Usenet system. De facto standard for handling news routing, news spool and serving the spool to customers. Available for various versions of Unix from the Internet Software Consortium. How-To's and mailing lists.
   http://www.isc.org/sw/inn/

Leafnode
   Easy to use, open source, IPv6-capable NNTP news proxy for Unix/Linux systems, designed for small networks.
   http://www.leafnode.org/

MPNews
   Modular Windows software. Supports full news feeds, web and RSS interfaces and automatic filtering. 30-day trial version available.
   http://www.mutantpenguin.co.uk/mpnews/

Mib Software NewsrA+e
   A subscription service to measure how well your newsserver is receiving articles. Benchmark against other servers to determine whether you are receiving and delivering "full feed" Usenet content in the groups you carry.
   http://www.mibsoftware.com/userkt/newsrate/

NNTPCache
   A cache server for Unix platforms. Free to use for individuals, non-military, non-profit research groups, non-profit organizations and medical or educational government departments. Others are required to license the software.
   http://www.nntpcache.com/

NNTPRelay
   The only carrier-class news router for Windows NT. Freely available and redistributable. Also available from the same authors is the freely available news server program "Tortoise" for Windows NT.
   ftp://ftp.tin.org/pub/news/servers/nntprelay/

NewsCache
   Usenet News cache server for Unix. Distributed under the GNU Public license. Reduces required network bandwidth of the news server. Multiplexes between different news servers and allows offline news reading.
   http://www.linuxhacker.at/newscache

NewsPlex
   Personal server utility which allows any news-reader to access several news-servers simultaneously, by merging their content into one single news-server. Freeware for GNU/Linux, Solaris and Windows.
   http://home.pacbell.net/robbie22/NewsPlex/

Papercut
   Open source news server written in Python. Its main objective is to integrate existing web based message board software, like Phorum which is supported, with a Usenet front-end.
   http://pessoal.org/papercut/

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://oss.basjes.nl/SuckMT/

Tortoise
   Freely available news spool server for Windows NT, based on the NNTPRelay program from the same authors.
   ftp://ftp.tin.org/pub/news/servers/tortoise/

Wikipedia: News Server
   Presentation of news servers and explanation of differences between transit, reader and hybrid (also called "sucking" or cache) servers.
   http://en.wikipedia.org/wiki/News_server

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://patrik.infa.fi/sn/