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.
Workona - A better way to work in the browser.
Session Buddy - Manage 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.
Raindrop.io - All your articles, photos, video & content from web & apps in one place.
Sidebery - Manage your tabs and bookmarks in sidebar.