Nzbperl - Open source, NZB based, command-line Usenet downloader written in Perl. Runs under several flavors of Unix including Mac OS X and also under Windows via Cygwin. - http://www.noisybox.net/computers/nzbperl/
Hellanzb - Open Source application able to retrieve nzb files and fully process them. Mac OS X and FreeBSD versions are supported, and there is also an unsupported Windows version. - http://www.hellanzb.com/
XPN - Open source newsreader for Windows and GNU/Linux. Supports scoring, off line reading and X-Face headers. - http://xpn.altervista.org/
Tamava Reader - Freeware news client for binary newsgroups only. Designed for Windows XP, Vista and GNU/Linux, it requires Java runtime environment. - http://www.tamava.com/
Binbot - Commercial binary newsreader for Windows and GNU/Linux. A limited demo is available. - http://binbot.com/
Pan - Open source newsreader designed for both text and binary newsgroups. It supports offline reading, scoring, killfiles, and multiserver access. For Unix-like operating systems and Windows. - http://pan.rebelbase.com/
Binary News Reaper - Also known as BNR, this is an open source, NZB capable news client for binary newsgroups only. Two detailed user guides are available on the website in PDF format. For GNU/Linux, Windows 95 and above. - http://www.bnr2.org/
NewsCoaster - Open source offline and online newsreader for the Amiga. - http://newscoaster.sourceforge.net/
SLRN - Threaded, text based, open source newsreader for Unix, VMS, OS/2, and Win32 systems. Highly customizable. Allows to redefine keys and to write custom macros. Full support for scoring articles, complex filters and killfiles. - http://slrn.sourceforge.net/
Good Net-Keeping Seal of Approval - Certain minimal standards for writing and evaluating Usenet software that conforms to netiquette. Ratings of newsreaders and of a few web-based ways to gain access to newsgroups. - http://www.xs4all.nl/~js/gnksa/
NewsReaders.com - Explanation of Usenet and list of newsreaders and other Usenet-related software. Directory of newsreader software sorted by operating system with brief descriptions and links to official download sites. - http://www.newsreaders.com/
Diiva - A newsreader designed for browsing encoded pictures in newsgroups. It allows you to see previews of images before they're downloaded. Available for Mac and Windows. - http://www.diiva.com/
Mozilla Mail/News - Technical information and project documentation of the integrated email and news client in the Mozilla Suite. - http://www.mozilla.org/mailnews/
CancelMoose[tm] - Information about the NoCeM protocol in general, including a listing of news clients which understand NoCeM, a protocol for reducing spam and other undesired Usenet articles. - http://www.cm.org/