Bitly.com is one of the tools I frequently recommend to students in my social media classes, in particular when discussing measurement and review. The service does so much more than just give you shortened links to use in Tweets, especially if you create an account — it gives you statistics on how many clicks your content is generating, when and from where (and that’s just that start).
This video from Digital Marketer gives an in-depth look at how they use Bitly, the types of info they gleam from it, and advanced techniques you might consider in your usage. Check it out.