The value of a link is a highly subjective assessment due to the large number of variables involved. One aspect to the power of a link is the site’s backlinks. The first tool I run on a site to help determine the value is Link Harvester created by Aaron Wall of SEO Book. It gives an estimate of the number of links to a specific page or domain based off of Yahoo.

Important Backlink Information it Displays

-Number of Unique Linking Domains
-Number of Unique Class C Blocks
-Number of .Edu Links
-Number of .Gov and .Mil Links

Here is a screenshot of Google Engineer and Spam Fighter Matt Cutts blog. Easily you can see he has backlinks from 1 college, 692 unique domains on 508 unique class C blocks. (Nice Job Matt!)

I suggest you experiment with Link Harvester on your favorite domain to discover all the features and uses. This is the tool I use the most each day.

Note: Link Harvester is Open Source and you may host it on your own server.