Bit.ly is a link shortening service used by millions of people to share the links across different platforms like Facebook, Twitter, e-mail and so on. If you add a + to the end of any bit.ly URL, you can see stats about that link. For example: here are stats for the shortlink we generated for our games http://bit.ly/15udmrF+.
Many online services use Bit.ly so if you want to check out the stats for f.ex. most popular Kickstarter projects just find a Bit.ly link (click on “Embeded” clause) and add + to the end. A great way of analyzing your competitors and where they are getting people from.