Google Toolbar for Internet Explorer (Only!)
Google toolbar - once installed - will give you the PageRank for any website, plus provide a quick and dirty check on incoming links to that site.
Install it, then click on the wrench icon, and be sure to turn 'on' the PageRank feature.
PageRank, of course, refers to Google's estimate of a web URL's 'authority' on the Internet.
Tags: google, link-building