There is an interesting map called “Geo-Geneology of Irish
Surnames”. http://tinyurl.com/y8hs9sw In the 2009 ESRI
International User Conference it won two awards in the Map
Gallery Competition. It was placed first in the “Most Unique”
category, and it won the People’s Choice Award. In addition, it
received special recognition by the Cartography Special Interest
Group. It was compiled by Dr. Kenneth Field, Principal Lecturer
in Geographical Information Systems at Kingston University
London, and Dr. Linda Beale a Research Fellow in the Department
of Epidemiology and Public Health at Imperial College London. As
you can see from the legend, this map shows the number of people
in 1890 who had various Irish surnames. The larger the font, the
more people who had that surname. You can read more about it at 
http://www.esri.com/mapmuseum/mapbook_gallery/volume25/cartograp
hy/cartography-1.html and download a copy of the map at http://w
ww.esri.com/mapmuseum/mapbook_gallery/volume25/pdf/mapbook25_22.
pdf