Feedreader is a lightweight open-source aggregator that supports all major RSS/ATOM formats.

Features
Supports all major syndication formats: RSS 0.9, 0.91, 0.92, 1.00, 2.0 plus Dublin core and Slashback extensions
Pre-configured with hundred of quality feeds from leading syndicators such as NewsIsFree and Moreover
Alerts about incoming feeds on taskbar
Caches headlines for offline viewing
Supports proxies
Allows one-click subscription of Radio Userland and AmphetaDesk feeds
Search support
Multilanguage support
OPML import and export.

What's New
Offline support added - Read more from here
Faster update intervals possible - Read more from here
Upgraded to new FirebirdSQL version. This version is faster and more stable.
Fixed bug with enclosure/podcast download when using some proxy servers. Previously download progressbars were left open.
Added twitter search feed
Proxy configuration added to welcome dialog.
Performance improvements because we eliminated some functionalities in RSS engine (Newsbrain) that were not needed in standard Feedreader.
Added a /debug parameter that can be used to debug Feedreader in case of problems.
Updated tree component that we are using inside Feedreader.
"Keep application in front when opening links in browser" is fixed
Translation files now support latest User interface features
Some little (and old) bugs fixed
Fixed some bugs with chunked download
"Smartfeed not saved" bug is fixed!