It's tough to measure, because you can't really know for sure how much traffic a site is getting unless you are the owner of that site. However, services like Alexa attempt to estimate the most trafficked sites by tracking segments of users (in Alexa's case they track users of their toolbar). Their top-site estimates can be split by country:<p><a href="http://www.alexa.com/topsites/countries" rel="nofollow">http://www.alexa.com/topsites/countries</a>