Robin Good: The Facebook Share Counter is a free web-based tool that allows you to check how many Facebook Likes, Shares and Comments any specific URL has received.
"Facebook allow you to measure the effectiveness of sharing links, by giving detailed data about how many times a url has been shared, clicked and commented.
With Facebook Share Counter you can now discover these details about any url you want, just input here the url (without any http://), and click get data."
The tool requires no registration or login and si free to use.
Try it out now: http://www.emetello.com/facebook-share-counter/