Foursquare Check-ins: See How People Move
One of the most enlightening collections of heat maps in recent months, these video heat maps show Foursquare check-ins in major global cities such as San Francisco and Chicago. In London, you can see how commuters flock to the center of town. In Tokyo, there's an obvious influx on trains that arrive right on time.
The data is used mostly for information purposes to show how many people are checking in, but city planners could use the data to see traffic movements or where to better direct services.