Probably most of bit.ly popularity comes from it's analytics, but if you have a lot of links, it's somewhat difficult to get an idea on your overall stats for a certain period of time. But now, bit.ly added a new Click Summary:
This is not just the number displayed on top of the page (featured in the image above), but clicking it, you will be redirected to a whole new page which allows you to see the stats for a certain period of time; but for now, it only works with the past 7 days.
Along the top of this new page, you’ll see a bar graph showing your aggregate clicks over each of the last seven days. Next to that, you’ll find pie charts showing Top Referrers and Locations for your link data. Finally, below that is a huge list of referrer and country data for the set time period (again, in this case, a week):
The referrer list is particularly interesting because it gives you a good sense of which Twitter clients are most popular among the people that click on your links.