GreatNews is an Open Source RSS feed reader for Windows.
GreatNews is designed with efficiency in mind and is written in C ++. Its features are decent enough for the average user, but it does not offer synchronization with Google Reader and lacks some flexibility when it comes to personalizing keys. The interface is a little dated but more than usable. There is support for newspaper reading topics, varied statistics, a search function that works well, and a high degree of compatibility with most other feeds, due to a large extent being a Unicode application.
RSS Guard is an RSS/ATOM feed aggregator developed using the Qt framework and supports online feed synchronization. A zero-dependency portable version is also available.
Royal RSS Reader allows you to read posts on RSS feeds and check them on startup and, if you like, periodically for new posts on RSS 0.91/0.92/1.0/2.0/Atom feeds.