Every ten years, the United States embarks on a census to count every person in the country. The 2010 census date of counting is only a couple of weeks away (April 1st, 2010) so there has been a lot of census talk in the media recently.
Erek Dyskant submitted his Census Data Explorer project as part of the Sunlight Labs "Apps for America" challenge. While only a few layers (poverty and race) are available so far, this seems to be a relatively fast browser for visualizing census data at the tract or neighborhood level. It appears to be using OpenLayers and Google Maps, and of course the data comes from the Census Bureau. Good luck, Erek!