The Mozilla Foundation offers not only firefox, but also thunderbird - a mail user agent. And the community has already developed several thunderbird addons for managing the Google synchronization:

Contact synchronisation

• A recommended open source extension is Zindus. After having updated onto Lycid Lynx the integration works very simply: download the extension file, import the extension using the thunderbird addon management, configure the gmail-account and synchronize both parts.The result is fine.
• Another well appraised extension (which I didn't test) is the addon Google Contacts.
• And a promising also untested addon in an early state is gContactSync.

Calendar embedding

• A simple solution is offered by ThunderCal: This addon integrates a button leading to the same internet-interface of google-mail which we already know from firefox.
• One extension which tries to connect Google calendar and Thunderbird seems to be the Provider for Google Calendar. But this extension seems to be no longer offered for the Lycid Lynx version of thunderbird.