Rated 4 out of 5 stars

le ander ar Iúil 11, 2009 ·

In FF 3.5, you can open a duplicate tab by holding Ctrl and dragging the tab to an empty place on the tab bar. You can also open the tab in a new window by dragging it into the content area.

Mike DePetris has also released a 3.5-compatible version of this add-on, which you can find on one of the add-on's MozillaZine pages:

http://forums.mozillazine.org/viewtopic.php?f=48&t=83785&start=165

I think he's simply changed the FF version number in its script, but I've installed it and it works great.