When was the last time you looked at the US Census American FactFinder? You might find some useful data if you ever use GIS to answer questions or even if you use GIS to come up with more questions.
TIGER files that show geographies across the country, the amount of tabular data available is huge. You can find information on local economies, household data, demographics, and more.
It might take a bit of trail and error to figure out the download process, but give it a chance and you might discover something useful.