I want to share with you a useful post I found on the Warrior Forum.

A user asked for suggestions about Firefox addons that can be useful in internet marketing.

The other users of the forum provided many good resources.
Some can be very helpful for SEO, but are listed also addons that refer to AdSense, Gmail and other ones that are not related to Google but surely can do some nice work for you.

Here is the link to this thread of the Warrior Forum:

http://www.warriorforum.com/main-internet-marketing-discussion-forum/8816-firefox-great-addons.html