The MIT SENSEable City Lab, in partnership with BBVA, visualizes spending in Spain during Easter of 2011. The animation shows the activity of 1.4 million people and 374,220 businesses, over 4 million transactions.
The map is less interesting to me since I'm a non-Spaniard (population density?), but the categorizations and spending volume over time is fun to see. Groceries are shown in blue, gas stations in yellow, fashion in pink, and red in bars and restaurants. During the day, you see people filling up the tank, and then as evening comes, the city centers and coast lights up red.