If you are curious to know which states in America or Canada have the highest density of people who have the same surname as you, check out the surname maps at Dynastree.
Geographic Distribution of people with the surname "Patel"
You type in a surname and with a click, Dynastree surname map will show you how people with the same surname are distributed across the country. The service is able to plot these surname distribution maps using the public phone book entries of the various states.
Maybe if you are planning to relocate, this service will help you shortlist the most immigrant friendly states in the US or Canada. Or you could even use the tool for some kind of family research if you have a very unique surname.
Other than America, you can also use Dynastree to plot concentration of residents with a particular surname across Canada, Germany and Switzerland.
And like Google Search, Dynastree is pretty intelligent at recognizing surnames that may be similar but have different spellings – for example, "agarwal", "agrawal", "aggarwal", "agarwala" are the same.
Also see: Make a Family Tree in Microsoft Office