Hit counters allow you to have numerical data about how many people have hit your site. These are the simplest kinds of trackers. We have a couple of examples on this page but specifically for this post I created one with the site: www.easycounter.com
A more complex type shows you approximately where people are coming from. These maps usually also have a visual representation of how many people are visiting the site. www.clustrmaps.com and www.feedjit.com both have these maps available as code you can install on your own webpage.
Finally, you can achieve higher level analysis of your web traffic with an analytics tool. Feedjit has options that show you where a visitor arrived on the site from, and where they exited too. Google Analytics one of the tools available with a Google account will also allow you to track how long people remained on the site before leaving. So, go find out if people are really reading your stuff.