Simple Tab Groups - Create, modify and quick change tab groups. Features:
Workona - A better way to work in the browser.
Simplified Tab Groups - This Firefox addon provides tab grouping features similar to the removed TabView/TabGroups/Panorama...
Session Buddy - Manage Your Browser Sessions
Panorama View - Tab Groups with Panorama View. Lets you easily Group and manage Tabs visually, with tab hiding.
Toby - Better Than Bookmarks