Review for Toolbar Buttons by Ben Harrison
Rated 5 out of 5 stars
Excellent! I haven't tested (and don't use) the majority of the new buttons, but a few are extremely useful.
In particular, the new 'Extensions' button is the only way (that I know of) to open Firefox 4's new Add-ons Manager in a smaller window rather than a new tab. In case anyone's interested, I wrote about it in more detail on my blog: http://darklythroughglass.blogspot.com/2011/03/firefox-4-add-ons-manager-update.html
Thanks!
To create your own collections, you must have a Mozilla Add-ons account.