Tabs Outliner - Next Generation Session, Windows, Tabs Manager and a TooManyTabs Solution That Really Works.
poll.ly - your perfect partner to gather ideas and opinions in real time
Tree Style Tab - Tree Style Tab is an all-in-one Firefox extension that provides ability in order to operate tabs as a tree.
poal.me - Free, realtime, configurable, user created polls with pie charts as well.
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.
Poltr - A modern, easy to use straw poll website that's completely free and doesn't require sign up.