Cool app. And a cool tool!

The Community GEO IP Project is a cool web-based app. Given an IP address, it maps it to a country/region - a highly useful thing for targeted applications! And an add-on tool for mozilla/firefox/descendents makes it immediately usable for individuals as well!
Keep in mind, though, that for a lot of unknown mappings, it depends on user feedback/input to update its database. So, you could, if you wish, help them correct their database if you find any problem. Of course, that is entirely voluntary, and if you are not scared by privacy issues etc.
A snapshot of the moz-plugin is included.