The U. S. Census Bureau's homepage for population, housing, economic, and geographic data. it includes Industry Quick Reports, Geography Quick Reports, and Thematic Maps.
"The American Time Use Survey measures the amount of time people spend doing various activities, such as paid work, childcare, volunteering, and socializing."
North Dakota's official source of population and socio-economic statistics. Has some good North Dakota stats at the state and county level (for the city/community level, see link below)
An incredible number of business statistics are available through BLS, including Employment Projections, County Wages, Pay and Benefits data, and information from the Occupational Outlook Quarterly
The National Federation of Independent Business operates 411 Small Business Facts to provide statistical information on a variety of topics related to small businesses
Though very useful for professional marketers, especially those in the media field, Nielsen is not free and does require a paid account (the library does not subscribe)
The Pew Research Center is a very well-respected gatherer of demographic data. Here you will find information on a wide variety of topics. Look at the Projects for specific niches (Internet users, Hispanics, etc)