http://tools.seobook.com/seo-toolbar/
Aaron Wall of SEOBook fame releases the SEO Toolbar.
The add-ons SEO for Firefox and Rank Checker are already part of my standard kit, this is certain to be too.
“Want to know why Google or Yahoo! ranks pages? If so this is the Firefox extension for you. The SEO Toolbar pulls in many useful marketing data points to make it easy get a holistic view of the competitive landscape of a market directly in the search results.”