From the site:
"Sage is a lightweight RSS and Atom feed aggregator extension for Mozilla Firefox. It's got a lot of what you need and not much of what you don't. * Reads RSS (2.0, 1.0, 0.9x) and Atom feeds * Feed Discovery * Integrates with Firefox's bookmark storage and Live Bookmarks * Imports and exports OPML feed lists * Newspaper feed rendering customizable via style sheets * Technorati and RSS search engine integration * Support for the following locales: Argentine Spanish, Catalan, Chinese, Czech, Danish, Dutch, Finnish, French, German, Greek, Hungarian, Italian, Japanese, Korean, Polish, Portuguese, Russian, Serbian, Slovenian, Spanish, and Swedish"