SEO Comapny has a free firefox plugin that rates the `inbound link quality` of the site you're currently visiting. I just installed it and it's pretty cool Click here for a mini screen shot.
I think they say @ the page what they use to determine link quality. BTW You have to restart fire fox before the plugin takes effect.
LOL ya I totally love all the extensions available for firefox. But I wish this computer had more memory so I could run them all I only got 256 MB or RAM on Windows XP