I have been using SEO quake since I first discovered the software it is probably the best Firefox plug in I currently use.
It allows you to view loads of different parameters for websites this includes the pagerank of the website you’re currently surfing, the Alexa rank, the amount of yahoo links the site currently has. There are a vast variety of parameters that you can currently add to the SEO quake toolbar they are easy to install and take a couple of seconds.
You can find out more about SEO Quake here and download it
http://www.seoquake.com/
