RSS Bandit is an Open source desktop news aggregator written in C#.
Instances of the program can be synchronized using WebDAV, FTP or a file share.
Single-click automatic discovery of RSS feeds. Ability to post comments to weblogs.
Support for tabbed browsing using embedded Web browser.
Support for password protected feeds using SSL & HTTP Authentication.
Look of news items displayed in the feed pane can be customized using XSLT.
Ability to flag items for followup.
Ability to track related news items and displaying them in a threaded view akin to a mail or news reader.
Read more here.