Swivel is a great data source for students and teachers alike. You can create graphs right on swivel or download the data sources and create your own. The data set shown in the link is food expenditures at home and away from home by year since 1933. I really like the food expenditures away from home since 1947, it looks like a nice exponential decay function. It would be nice to have students analyze what happened in 1947 to cause the graph to change its behavior. If you are a SS or American History teacher, I think looking at the initial aspect of this data would be interesting given that the data mirrors the great depression and as America came out of the depression the amount of money spent on food items at home decreased, until the advent of WWII!