Welcome to Like Explorer. This cool website allows you to enter in the url you are interested in and see which social channels it has been shared on. It also features how many Facebook Likes, Comments and Shares the link has received.
I stumbled on this tool while exploring some articles from Social Media Today. It is a really great way to see where people are talking about your site. While, it's a great benchmark, it doesn't allow you to see when and who specifically shared the link - that's where more advanced tools come into play. Happy searching and hope you find this information useful!