Review for Duplicate Tab by Empatojayos
Rated 5 out of 5 stars
I posted a working add-on for Firefox 5. (I modified the original, now accepts Firefox to v5.9)
http://www.megaupload.com/?d=U9SIHQSZ
(Tested in FF 5 beta 5)
To create your own collections, you must have a Mozilla Add-ons account.