Most people have some idea of where their ancestors emigrated from. If not, last names can give hints. This website mapping the location of last names creates maps showing where in the world certain last names exist.
You can enter any last name and find the prevalence of that name throughout much of the world. Not all countries are represented, but it is worth experimenting with.
The above image shows prevalence of my Grandmother's maiden name in Europe. You can look at the world view, continent view, or in the US you can even view occurrence of names summarized county.