This website will tell you the frequency of occurrence for any name in the USA. Type in a name and it will report how many people in the US have that first name, that last name, and how many have both names.
HowManyOfMe.com might just be a quick bit of entertainment. It boggles my mind to see that there are 85 other people in the states with my full name. But I can also see this being a useful tool for anyone choosing a stage name or pseudonym.