This is a pretty cool use of Google Maps. You tell it the URL of your site, and it gives you a small piece of Javascript code. You stick that in the <head> section of your site, and it will plot where your site visitors are on a Google Map. Here is the map for my personal site.

If you stick with the free version, it maps only the 20 most recent visitors. You can make a donation of any amount and get the 100 most recent visitors. You can even tweak the URL of the map page to show IP addresses.

Hat tip Ian