Social Crawlytics uses Twitter authentication to scan public websites and provide a report
You have a dashboard, history of reports and a great visual showing page shares per social network. Using the graphs and information you can see which of your pages are the most shared across social networks and influential on your own or any public website.
I an a report against EverythingTwitter to see how we do and it was amazing to see how our most popular places shared is StumbleUpon and Twitter. The reports can be expanded by clickin on them to get more detailed information.
This is a tool I am adding to my list to run against all my sites. They have free (with some limitations) and paid accounts.