Enter a surname (last name) into the World Names Profiler, and get a choropleth map showing the population density of that name:
A table of the countries with the highest FPM (frequency per million) of that name:
Click on a country, and get a more detailed choropleth map for that country:
And more info:
Coverage is spotty; Europe and North America are well-covered along with Australia and New Zealand, while Russia and China have no data. South America has only Argentina, and Asia is spotty (only India and Japan appear to be covered).