The United States Census Bureau has some terrific information that goes beyond counting the number of bodies in the United States.
I thought the Population Clock was interesting to see--for one factoid. I also did not realize that the U.S. is the third most populous nation in the world, and that Indonesia is the fourth.
You can get a bunch of information on your state by selecting it and running down through all the tabulations.
There are going to be legislative census wars in the months to come. The first rounds have already been fired. Who gets counted and what information is gathered will be the issue.