SplitUp! - A fun and elegant tab manager
Simple Tab Groups - Create, modify and quick change tab groups. Features:
Tab Stash - Tab Stash is a browser extension that helps you keep your tabs straight, saved, and restore them later.
Panorama View - Tab Groups with Panorama View. Lets you easily Group and manage Tabs visually, with tab hiding.
Smart Tab Manager - Smart Tab Manager is a browser extension that allows you to save & restore your browser sessions.
Tree Style Tab - Tree Style Tab is an all-in-one Firefox extension that provides ability in order to operate tabs as a tree.