The Wizz RSS News Reader, is a very simple RSS (Really Simple Syndication) and Atom news aggregator. It is an XUL application, implements as a Firefox extension and is absolutely 100% free of charge. Wizz RSS does NOT contain ANY spyware or adware.
FeedOnFeeds-Redux (FoFRedux) is a continuation of the popular, but stagnated FeedOnFeeds project. FoFRedux provides a simple, yet effective browser-based news aggregator.