Just now i added the clustr Map to my blog. It shows from where visitors came to your site. Thats a good one....it will be rather a good indicator of the peoples intrests in various topics. The free version can be got very easily just paste the html code and its done.
You can get your own at http://clustrmaps.com/index.htm . It looks something like the picture when you zoom in. It nicely fits into your sidebar. The worlds longest sidebar suerly needs this one.
"See at a glance where your site's visitors are located: instantaneously, even when the numbers are enormous! Visitors don't need to click on anything: just viewing your page is sufficient."