According to the U.S. Census Bureau's most recent geographic data (1993), the most common street name in the U.S. is "2nd" (or "Second") Street. Although many cities have a set of numbered streets at their core, it is common for one or several of those those central streets to be renamed in honor of a historic figure, such as George Washington.
This list enumerates the twenty most common street names and the number of nationwide occurances:
The Census Bureau mentions a point of statistical note in the report: a town with an "East Main Street" that continues onto a "West Main Street" is counted as two separate streets.
U.S. Department of Commerce, Bureau of the Census, Geography Division. Census and You. Washington, DC: U.S. Department of Commerce, Bureau of the Census, Geography Division, 1993.