TALAggregator

Multi-user web based RSS Aggregator. Caches feeds to MySQL database, handles bad RSS, and includes template driven interface.
http://www.owlfish.com/software/TALAggregator/

AmphetaDesk

Free, cross platform, open-sourced, syndicated news aggregator.
http://www.disobey.com/amphetadesk/

Radio Userland

News aggregator included with weblog software application for Macintosh and Microsoft platforms.
http://radio.userland.com/

myRadio

Extension to Radio Userland aggregation from RSS to any data source, including XML, HTML, and SOAP.
http://radio.weblogs.com/0100875/outlines/myRadio/

BottomFeeder

A Smalltalk, desktop RSS Reader. Open source, runs on Windows, Mac, and various Unix flavors.
http://www.cincomsmalltalk.com/BottomFeeder/

TheYoke

A simple RSS aggregator designed for use on the UNIX command line.
http://www.mackers.com/projects/theyoke/

JavaScript RSS Reader

Downloadable script for reading RSS 1.0 and RSS 2.0 feeds.
http://www.qiksearch.com/javascripts/rss-reader.htm

Parss Project

The general idea behind Parss is to solve the problem of countless individual (desktop) RSS viewers randomly and redundantly transferring and processing almost exactly the same set of RSS feeds.
http://weblogs.at/parss/

Rnews

Server-side RSS aggregator written in php using MySQL as the back-end and uses magpierss for the RSS parser.
http://rnews.sourceforge.net/

Raggle

Open-source console-based RSS aggregator, written in Ruby, for Linux, Unix and Windows. Information for users and developers.
http://www.raggle.org/

phpNewsfork

Browser-based news channel and Weblog interface based on PHP, XML-RPC, and RSS. It uses the XML-RPC APIs from meerkat.oreillynet.com and syndic8.com, and does not require a database.
http://www.borho.net/news/about.html

NewsFeed

A desktop RSS reader and aggregator in Python/Tk.
http://thor.prohosting.com/~mdoege/newsfeed/

News2Web

Takes a set of newsfeeds and publishes a webpage from them. Designed for corporate users.
http://www.hexamail.com/news2web/

Jyte

Cross platform news reader with RSS and Atom support, as well as news from major news sites and keyword searches.
http://www.jyte.com/

CafeRSS

Information and download for an RSS aggregator using PHP.
http://barkerjr.net/webdesign/

FIRST SAY

Open source RSS news aggregator designed to build collections of feeds and provide a first page presentation of feeds from many sources.
http://www.firstsay.org/

Aggreg8.net

RSS feed aggregator built on the Mozilla framework or XPFE. It uses XUL, Javascript, RDF, CSS, XPConnect, and XPCOM.
http://www.aggreg8.net/

Mercury News Readers

Displays RSS, RDF and Atom feeds. Available as screensaver, news ticker, Internet Explorer toolbar, and feed reader application.
http://oracle.2question.com/rss

Sage

RSS and Atom feed aggregator for Mozilla and FireFox browsers.
http://sage.mozdev.org/

DogWalker

An extension to Adam Simpson's RawDog (web based aggregator python script). DogWalker is a script that periodically runs RawDog on webmaster's home PC and ftps the result to the site.
http://rawfish7.tripod.com

Urchin RSS Aggregator

Perl, web based, customisable, RSS aggregator and filter that consumes RSS, Atom and screen-scraped HTML and produces RSS or XSLT-transformed output.
http://urchin.sourceforge.net/

Wizz RSS News Reader

A simple RSS news reader extension for Firefox. Reads all versions of RSS. i.e. 0.90, 0.91, 0.92, 0.93, 1.0 (RDF) and 2.0.
http://www.wizzcomputers.com/WizzRss.php

MyHeadlines

Content syndication search engine and news reader that can be integrated into a website running PHP and MySQL.
http://www.jmagar.com/myh4

Planet

Server software that combines several feeds together and publishes them together on one web page.
http://www.planetplanet.org/

QuikView Channel Viewer and Bookmark Server

Full channel RSS / XML viewer and bookmark server. A portable, cross-platform, sidebar application. Able to read all RSS versions.
http://quikonnex.com/quikview/triizine/index_bottom.php?customname=triizine

Pluck

A tool that automatically retrieves RSS feeds then delivers the results for scanning and customized sorting.
http://www.pluck.com/

RssDisplay

A quick Perl CGI to render an RSS feed in HTML for use in SSI on sites. This script does that very simply, yet with a small set of configurable options.
http://www.decafbad.com/twiki/bin/view/Main/RssDisplay

Gush

Combines Jabber instant messaging with news aggregation and a split chat feature. [Windows, OS X, Linux]
http://www.2entwine.com/

Feed on Feeds

A Free PHP/MySQL based server-side RSS and Atom aggregator. All feeds are in one place, and users can read the latest news wherever they are.
http://feedonfeeds.com/

BlogMatrix - Jäger

RSS syndication reader that uses a web browser to display content. Jäger runs on both Windows and Macintosh OS 10.3.
http://www.blogmatrix.com/products_jaeger/

Pears

Three-pane newsfeed (RSS/RDF and Atom) aggregator which caches downloaded feeds for offline use. It has a clean interface, and works on Windows, Linux and Mac OSX.
http://project5.freezope.org/pears/

Blagg

News aggregator for the Bloxsom weblogging system.
http://www.raelity.org/lang/perl/blagg/

Peerkat

Cross-syndicated personal syndicated news aggregator for use with Python.
http://www.raelity.org/lang/python/peerkat/

Rocketinfo Desktop

Search software for finding and sharing news with integrated solid RSS newsreader.
http://www.rocketdesktop.com/

Rawdog

An aggregator written in Pythonthat supports RSS 0.9, 1.0, 2.0, CDF and Atom feeds.
http://offog.org/code/rawdog.html