iGoogleBar Firefox add-on supercharges Google apps bar
iGoogleBar is a Firefox add-on that adds a little oomph to that menu bar by showing previews for each Google app. For example, if you're using Google Docs & Spreadsheets, you can tell at a glance how many unread items you have in Google Reader or Gmail. Or you can click on the icons for a preview of your latest messages.
The toolbar only shows up when you're visiting a Google page, and it doesn't work with all Google services. For example, while you can preview your Google Notebook contents, when you're actually on the Google Notebook page the toolbar doesn't show up. It also takes a moment for the toolbar to load, so you might not notice it at first.