Shazam is a service with an app that lets you point your phone towards some music to identify the name and artist of a song. For a hack day, Umar Hansa mapped a billion recognitions. Some of the maps color-code recognitions by iPhone and Android use which is kind of interesting.
Hansa used Eric Fischer’s datamaps, in case you’re interested in making your own.
Visualize This: The FlowingData Guide to Design, Visualization, and Statistics (2nd Edition)
