Subway Sparklines [transit.frumin.net] illustrates the relative yearly ridership of every New York City subway station from 1905 until 2006. Each station is represented as a separate sparkline, located on the New York city map. The general idea it that the history of subway ridership tells a story about the history of a neighborhood that is much richer than the overall trend. An example shows the comeback of inner Williamsburg, and how the growth decays at each successive stop away from Manhattan on the L train.
For more information, check out the map author's accompanying blog post.