Cool map from Pew shows the most popular website in each country, weighted by size of internet population.
Google dominates the developed world, but the developing world is very scattered between Google countries and Facebook countries. It looks a little like a map of cold war proxy wars. But the real cold war is between the Google zone and then the vast Chinese market which is dominated by a local company that's friendlier to Chinese censorship efforts. When Farhad Manjoo and I did our Apple/Google war games, this was a key point—Google seems ubiquitous and fully necessary, and then you realize there's a whole giant country where there basically is no Google.