The first part of the 2010 census was released today. Check out the website: 2010 Census. Data for individual locations is not yet available, but state populations are. The Census Bureau has to publish this information by December 31 so Congress knows how to apportion its seats in the House of Representatives. Click the Data tab and check out the map to see whether your state has gained or lost any seats.
For what it's worth the US has officially reached 300,000,000 residents.