To have the time of your life use Mutltiple Tab Handler with Tree Style Tabs Rated 5 out of 5 stars
Superb add-on for anyone who is used to opening many tabs in a single session. Indispensable. Use with Tree Style Tabs and you'll be hooked. Then you can close off Trees.
Great productivity add-on.
I ran it on Windows 7, now on Linux Mint 14. Well maintained, 0 problems.