Workona - A better way to work in the browser.

OneTab - Whenever you find yourself with too many tabs, click the OneTab icon to convert all of your tabs into a list. When you need to access the tabs again, you can either restore them individually or all at once.

Tablerone - Browser extension for saving, organising, and exporting tabs. Save multiple tabs with one click. Get more done with a clean browser.

Session Buddy - Manage Your Browser Sessions

Toby - Better Than Bookmarks

Tree Style Tab - Tree Style Tab is an all-in-one Firefox extension that provides ability in order to operate tabs as a tree.