This site contains extensive data on the social and economic characteristics of the population. Many more geographies can be searched, such as metropolitan areas and census tracts. You can use the "Community Facts" search box to find more detailed data about cities.
The American Community Survey (ACS) is an ongoing survey that provides vital information on a yearly basis about our nation and its people. Information from the survey generates data that help determine how more than $400 billion in federal and state funds are distributed each year. This essentially replaces the "long form" that used to be part of the decennial census.