bit.ly: tracking your short URLs

There are probably many tools out there, but if @mattcutts is using bit.ly, then it’s probably on the better side. When you’re signed in, you get your shortened url (e.g., http://bit.ly/10UdcG). I can now track when someone clicks on that short URL. I can see weird stuff like from what country, but I can also see useful stats like what site you clicked from (twitter, blogger, facebook). I can also see if someone else copied the URL into their own Tweet as well. Movie trailers seem to get picked up pretty well by others!