Try: http://www.census.go...tiger-data.html. It has geography down to the Census Tract. Two statements to be aware of:
"These national level shapefiles join the geometry and selected attributes from the 2010 Census TIGER/Line Shapefiles and the 2010 Census Summary File 1 Demographic Profile (DP1) for the United States and Puerto Rico. They contain data items such as total population, total housing units, median age, population 16 years and over, population 65 years and over, race, relationship, average household size, and many others. All files are zipped."
"These files lack metadata. Metadata for the shapefiles can be found in the 2010 Census TIGER/Line Shapefiles. There is an MS Excel file in each zip file that relates the short data table name of the demographic profile data element to its full name. For example, "DP0010001" is the short name for the data table containing total population. The attribute table for each shapefile contains the short names for each data element."