GNUzilla is the GNU version of the Mozilla suite, and GNU IceCat is the GNU version of the Firefox browser. Its main advantage is an ethical one: it is entirely free software. While the Firefox source code from the Mozilla project is free software, they distribute and recommend non-free software as plug-ins and addons.
Link to download: GNUzilla and GNU IceCat Open Source Web Browser (http://www.theinfostride.com/forum/index.php?action=downloads;sa=view;down=79)