Review for Duplicate Contact Manager by Egil Kvaleberg
Rated 5 out of 5 stars
The user interface and the logic of this gem of an add-on are both perfect. It is a wee bit slow with 500 contacts, but not enough of an issue to detract from its five star rating. If only the various address sync ultilities were as good as this one!
This review is for a previous version of the add-on (0.6).To create your own collections, you must have a Mozilla Add-ons account.