]Like most of the folks who've already replied to your question, I also use bit.ly with my own domain. If your intent is the shortest possible URLs and you don't care about using your own vanity domain, bit.ly also owns the "j.mp" domain, which can be interchanged anywhere you otherwise see "bit.ly".

However, if you're looking for more detailed metrics, you might also want to consider looking at some of the ad tracker tools internet marketers use, as they support features like advanced campaign management and duplicate detection.

hyperTracker (www.hyperTracker.com) provides some pretty detailed metrics, and they also provide guidance for using your own short domain(s) to masquerade URLs created with their service.