From time to time I mention new extensions I've acquired and something about how well they work. Today I want to mention the Gmail Notifier extension from Doron Rosenberg. I've been using this on and off since he first published it but now it's sufficiently matured that I'm adding it to my list of "permanent" extensions (along with Linky and Link Visitor). The extension is pretty slick with a toolbar button/notifier, a statusbar notification, a slide-up taskbar notification window (like Thunderbird or Firefox's download notification), automatic login, and some nice preferences for how often to check as well as where to load Gmail if you click the icon -- the same tab, a new tab, or a new window. The extension inherrits the users' theme style quite well and I've got no complaints with the feature set. If you've got a Gmail account (and several dozen of you should, since I gave them to you) then go give it a try. I think you'll like it.
