it really depends on what kind of "click tracking" you need. for example, you could very easily install a script that could count a "raw" hit...meaning anytime anyone clicks on the link it will increment the counter. then there are unique clicks, where you don't count it if you've already seen the IP or the cookie in a certain period of time.

i would also be very careful of what i call "Self-fulfilling Prophecy" -- sure, you want to display the banners or images that are most often clicked, but of course, the more you display a banner or image, the more often it will be clicked, even if it's a horrible banner, if it's displayed 99.9% of the time, then that's the one that is going to generate the most hits.