Joomla CountryBlock is a module that allows site owner to grant access to certain countries or block access from certain countries. If admin does not specify the redirect URLs for blocked or granted countries, visitor's IP address and country/flag will be displayed.
Version 1.2 is free. Free version is GPLed too.
This module has been updated to support Joomla 1.0x/1.5x/1.6x/1.7x/2.5x/3.0x. IP to Country data files are updated to Mar 2013.
I needed to block some countries for a technology site to reduce the chances of design ripoff and cloning. I paid my $10 for the extension, set it up in a matter of minutes on my Joomla 1.7 site, got a little mixed up with block and allow settings, mailed the developer and got clarification in under an hour. Works like charm and can also be run completely invisible.
I had some spammers coming in from another country, so with this module I was able to block them out. Of course they could use a domestic proxy server, but I use RS Firewall to supplement this. Really easy to set up, and if you publish the module to "show no country", you won't even see it on your page. Nice work. Thanks.