Commercial version: Google Reader, Bloglines
Open-source alternative: RSSOwl
RSSOwl is a simple and lightweight desktop feed reader. It offers multiple viewing options and easy importing of XML files.
The good: The 'Owl offers an uncluttered interface that allows easy navigation of multiple feeds. A Web browser is built in, so there's no need to leave the application to click through the Web sites. The application itself is extremely fast and very friendly, though rather basic, aesthetically. There's a feature that lets you enter a Web site's URL and RSSOwl will scour it for RSS feeds, which can then be imported with the click of a button. It's even possible to export all feed entries to PDF form for easy offline reading.
The bad: The built-in Web browser is Internet Explorer, raising the usual security issues common to IE.
Conclusion: Since you need to be online to use an RSS reader properly, RSSOwl is a great application. The ability to export feed items to offline documents could be a huge bonus over Web-based apps such as Google Reader.
Download it here: rssowl.org