Review for Oxford Dictionaries by Unindoctrinated
Rated 4 out of 5 stars
I've been using this for nearly two years and I love it. The search results may not be as fully featured as their subscription service or even Dictionary.com but at least it's in proper English not American English.
This review is for a previous version of the add-on (20100712).To create your own collections, you must have a Mozilla Add-ons account.