AgileRss - A free desktop aggregator that supports all versions of RSS and Atom. - http://www.agilerss.com/
TopFeed reader - A free reader that supports RSS, RDF and Atom based syndication formats. - http://home.iprimus.com.au/gautamsonu/topfeed/
Feed'n Read - Free Java based open source newsfeed reader. Supports all current formats (RSS 0.90, 0.91, 0.92, 0.93, 0.94, 1.00, 2.00, Atom 0.30 and 1.00). - http://fnr.sourceforge.net/
RSSOwl - Uses the SWT Eclipse library to provide a cross-platform desktop application to read RSS subscriptions. - http://www.rssowl.org/
BlogBridge - Windows, Mac and Linux based RSS feed reader, which is designed to allow users to easily manage and follow hundreds of feeds. - http://www.blogbridge.com/
Thinfeeder - Free, cross platform, multi-language RSS / Atom / RDF reader. Anti-aliasing, skins and multi-language support. Developed in Java, works under Windows, Linux, MacOSX and others. - http://thinfeeder.sourceforge.net/
RSS Viewer - A Java based, open source RSS reader. - http://rssview.sourceforge.net/
nntp//rss - Enables RSS feeds to be read with NNTP newsreaders. Requires the Java Runtime Environment. - http://www.methodize.org/nntprss/
NewsMonster - Mozilla and Java-based aggregator with RSS 2.0 support. - http://www.newsmonster.org/
JERSS - Allows seamless integration of RSS newsfeeds into websites. It is a Java servlet generating Javascript objects the web author can manipulate. - http://www.jayeckles.com/news/
Hotsheet - A Java based desktop newsreader. Works on Windows, Macintosh, Linux and anything else with a Java Virtual Machine. - http://www.johnmunsch.com/projects/HotSheet/
Flock - RSS aggregator written in Java. - http://flock.sourceforge.net/
curn: Customizable Utilitarian RSS Notifier - A Java-based extensible, caching RSS reader. Command-line utility, intended to be run periodically by a command scheduler such as cron(8) or the Windows Scheduler. - http://www.clapper.org/software/java/curn/