Review for GMail Labels by inknos
Rated 5 out of 5 stars
I love it. I use gmail filtering but I hate the web interface, so this extension serve the exact purpose of filling the gap.
A suggestion. It would be nice to see the labels before opening the message. Maybe, inline with the subject as gmail does OR in a separate column, so messages could be sorted. I am not sure how hard would it be to implement.
To create your own collections, you must have a Mozilla Add-ons account.