Review for Duplicate Tab by LukeCro
Rated 5 out of 5 stars
Easily one of the handiest Firefox add-ons out there -- quickly duplicate/copy/clone any tabs (including the page's full browsing history -- so you can browse Back and Forward within the duplicate), detach tabs into new windows, merge detached windows back together into a single window full of tabs . . . This should be built tino Firefox by default!
Here's hoping that a Firefox 3.5 version of the plug-in comes out soon. Firefox just isn't the same without this extension.
To create your own collections, you must have a Mozilla Add-ons account.