Here's a quick way to make sure you never need to open your Google Calendar in a tab again: Open it in your Firefox sidebar instead. Discovered at Firefox Facts, it adapts some code from iGoogle and streamlines it down to just the calendar. This is a great hack if you can't or won't use the Google Desktop Sidebar.
Log in to your Google account first, and then load up this Google Calendar link in a regular tab.
You'll see your Google Calendar load, but in what appears to be a stripped-down version. You can Quick Add events, Create events, and Hide agendas while the calendar shows you a multiday listing of your schedule at the bottom. Bookmark the URL, and then in your Bookmarks folder right-click on the bookmark and choose Properties. Select the Load this Bookmark in Sidebar and you're good to go. Whenever you click on your Google Calendar bookmark, it'll open in the sidebar.
Incidentally, this worked flawlessly with the All-in-One Sidebar plug-in, which gives you such a wide range of sidebar options that I've forgotten what the native Firefox sidebar is limited to.(From CyberNetNews)