Review for Gmail Manager NG by David Nir
Rated 5 out of 5 stars
The good news: This absolutely vital extension still works. The bad news: Snippets (the little pop-up boxes that show you who your new emails are from & their subject lines) that appear when you hover over the relevant account icons no longer work. I really love having snippets, since you can know at a glance whether or not it's necessary to actually log in and read/respond to your email, and I'd love to have them back.
To create your own collections, you must have a Mozilla Add-ons account.