Lot of stuff available with this. I had no idea there were this many services available.
I’ve only just started tweaking it but am liking it already for the easy access to my Google site and mail.

Display all Google services as buttons or as a space-saving dropdown menu next to your address bar.
Reach services like Gmail, Google reader, Google maps, Google calendar, and many more in a single click from your browser.”

Works with
Firefox 2.0a1 – 6.*

 Google Shortcuts – All Google Services at a glance :: Add-ons for Firefox

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