For a free tool, I’d say that Google Analytics does a great job for delivering stats of site visitors and their usage of your site. With this in mind, developers have created some great Firefox addons that will provide faster access to Google Analytics. Take a look at these for starters:
Check Current Day Google Analytics
Stats for the last 30 days is displayed as a matter of course in Google Analytics, but most webmasters are really interested in checking their stats on a daily basis to discover the amount of visitors they have attracted. Check out the Analytics Today Browser Bookmark for quick access to daily stats. As the bookmark will only work for one site at a time, try this Bookmark Generator in order to gain access to the stats of up to 10 sites at once.
This nifty plugin promises to deliver assistance to the webmaster by delivering more meaningful information for the set period of time requested. The tool not only enables export of data to a word document but will delivery Social Media metrics too. Delivery of social media mentions is available at the click of a button and will save you the time that would otherwise be spent visiting your social networking tools such as Social Mention. The icons are clickable so that you can go straight to the site and check out the mentions for yourself.
Use this tool to watch Google Analytics from your browser header. Just what every webmaster needs to keep a track on how well his or her site is performing.
Firefox has plenty of addons for many different purposes. Another one that you might consider using to aid with SEO is the NoDoFollow add on that will tell you whether a site has dofollow linking opportunities.