Vienna

Vienna is a freeware, open source RSS/Atom newsreader for the Mac OS X operating system.
It provides features comparable to commercial newsreaders, but both it and the source
code are freely available for download.

A summary of some of its features:

• Subscribe to Atom/RSS news feeds and podcasts.
• Simple and intuitive user interface.
• Built-in tabbed browser.
• Smart folders for organising related feed articles.
• Custom article display styles.
• Full AppleScript support.