Rated 4 out of 5 stars

HEY, check out the new built-in drag/drop tabs functionality in Firefox 3.5+... Grab a tab & drag it around... Hey, even drag it OUT of the browser to it's own new window (NICE!).

HOW TO:
You may duplicate a tab by clicking on the tab you want & holding the CTRL key (CMD key on the Mac). Then, just drag and drop it to where you want the new tab to appear... It works across Firefox browser windows, too. (In my tests, it even kept the text of this message AS I was still entering it.)