There are many problems you can't solve technically, but this question can answered easily.
We took the ip-to-country database by Directi.com and merged it with our old Apache log file. Put the resulting data into a PHP script and by the help of GD we produced these little pie charts.
Unfortunately we don't have Apache logs from before 2004 so we can't look further back in time. Last month's top 10 countries 2006's top 10 countries 2005's top 10 countries 2004's top 10 countries