INN (InterNetNews) is an extremely flexible and configurable Usenet / netnews news server. It supports accepting articles via either NNTP connections or via UUCP, as well as serving out articles to reading clients via NNTP. It supports multiple different ways of sending outgoing articles to other hosts, as well as multiple different storage mechanisms for articles and article overview information via internal APIs. Compared to other news servers, INN is more complicated with a steeper learning curve, but is extremely flexible and configurable, comes with a large suite of supporting programs, and supports embedded filters in either Perl or Python.
Papercut is a multi-threaded NNTP server written in Python. Its main objective is to integrate existing Web-based message board software (Phorum is one of the supported ones) with a Usenet front-end. However, its extensibility enables developers to write their own containers for the storage of the Usenet articles (messages). That means that the code is extensible enough that you could write new containers to integrate the news server with other Web message board projects or even other ways to store the messages.
X Python Newsreader (XPN) is a multi-platform newsreader with Unicode support. It has features like scoring/actions, X-Face and Face decoding, muting of quoted text, newsrc import/export, find article and search in the body, spoiler char/rot13, random taglines, and configurable attribution lines.
MessageViewer is a very simple GTK program that fetches and views one Usenet news message based on its message-id. Its main use is to quicky look at one article in cases where opening a real news reader and trying to locate it based on msg-id is too much of a hassle. It can also read the message-id in news:<id> or news:id URL formats, and can therefore be set to handle such protocol requests. It does not support authentication of any kind at the moment.
hellanzb is an application that retrieves and processes NZB files and makes obtaining files from Usenet as hands-free as possible. Once fully installed, all that is required is moving an NZB file to the queue directory. Downloading, par-checking, and un-raring is done automatically by the program.