Integrated Gmail is an addon for Firefox that allows you to make your inbox collapsible and load several other Google services like Google Calendar, Reader, Notebook, Groups, Maps, Picasa, Sites, News and Portfolio seamlessly into the Gmail interface below the inbox. You can choose which services you want to integrate and adjust the width of each added application. You can also add custom URLs with navigation buttons and Google Gadgets. Additionally, you can remove the headers from these application to make them compact and save space.
Integrated Gmail is an easy way to access all your favorite Google services from one place. Access Google calendar or read feeds or browse maps right from your inbox. If you don’t like the collapsible interface and rather have tabs, then wait for the next release of this addon, when this feature would be added.
Integrated Gmail works with Google Apps too.