The main tracker I use is AdTrackZ
Why ?
Read an extensive report here
* If you are tracking PPC ads you can also check for fraudulent activity with AdWatcher
* If you want to optimize your site conversion use KaizenTrack
* If you want to offer a tracking service to others whereby they can login and see their own reports look at ezTrackZ
If you are new to ad tracking and want to quickly check how it can be profitable for your business then you can sign up for a free trial version with a tracking service such as AdMinder or HyperTracker.