SEO plugin for Firefox
This is a great little tool to help save time when reviewing websites that compete against yours (or your clients site).
Just fire up firefox and browse over to http://tools.seobook.com/firefox/seo-for-firefox.html and follow the installation guidelines.
The tool will show up in search engine results pages, allowing you to see at a glance, the PR of a site, the age of the domain, the number of Yahoo! links, Del.icio.us links, Yahoo! directory listings and more.
Have a go, install it, use it see what you think!