Isn't it a pain having to open up a new tab or window every time you want to look at your Google Calendar? Luckily, for Firefox users there's the currently experimental Gcal Popup add-on which puts your calendar only a click away.
Once Gcal Popup is installed, a calendar icon will appear at the bottom left of the Firefox browser, and when clicked, an overlay pops up with Google Calendar. You have to log in, and there's no option to do this automatically, although if you're already signed in to Gmail, it's not necessary.
It's certainly handy to have Gcal sitting at the ready, and this experimental add-on seems solid. I was hoping for a Ubiquity-style partial screen pop up, but this is less polished. Hopefully this will change in later versions. Obviously, one drawback is you have to use Google Calendar - a working with other calendar applications would be fantastic.
Despite this, Gcal Popup's such a nice tool, making Google Calendar seem so much more accessible and useful, it's a highly recommendable add-on.
Gcal Popup is one of the most useful Firefox add-ons we've seen