A new Web tool called WhoReTweetedMe offers a summary of Twitter sharing data for any page.

These results show the Twitter activity over time for a recent Mashable story, as well as the total number of tweets and potential audience they reached.

After entering a page URL, you see a report of the timeline of tweets linking to the page, statistics about potential reach and average follower count of retweeters, creator Dan Zarrella explains.

There's even a list of the 20 most influential tweeters with a link next to each that lets you send them a thank-you message. It also has a bookmarklet for a one-click check of data for any page currently open in your browser.

There are a couple caveats. It's brand-new, and might still be a little buggy. And it works best with pages that have been active more than one day, but less than two weeks.