The Census guy came to our house yesterday. I listed my race as "some other."
Looking at the 2010 Census form, one wonders how and why they selected the racial categories and subgroups. There are seven racial subcategories for Asians, five for Pacific Islanders, and four ethnic subcategories for Hispanics. But no racial subcategories for Blacks or Whites.
Here's a partial answer to the "how and why" question.
Another thing that struck me as odd: the organization responsible for determining the categories is OMB.
UPDATE: Wikipedia traces the evolution of racial categories in the US Census from 1790 all the way to the present day, here.