I found this tool; Post trades; http://www.posttrades.com/forum/ through an seo blog by DazzlinDonna (SEO Scoop).

In the upper right hand corner of the page type in your url www. your domain.com and it reports some new different information,including number of backlinks reported by yahoo and the number of unique urls.

Adding unique urls as backlinks has been our primary focus to get higher in the google serps. It has slowly worked over time. We are now 6 for our primary keyword phrase. Because our url is www. keyword-keyword. our allinanchor is strong as is our allinurl.

As of today 1/2 of our total backlinks were unique urls. In the last 5 days this report has shown an increase in over 20 unique urls among bls reported by Yahoo. (That reflects Yahoo picking up new backlinks added over a couple of weeks) In fact without realizing it we picked up a sitewide the other week -only about 15-20 pages on the site.

I'm curious if others find that greater number of unique urls among backlinks dramatically helps them...and if they can measure the serps impact over time.

BTW we are #1 in both yahoo and current MSN for our main keyword phrase; 6 in google. We definately have a lot of on page optimization which everyone says is critical for Y and MSN, but I'm wondering if a diversity of urls for backlinks shows a positive impact?