Mapping Buildings in the Netherlands by year of construction
Beautiful map (http://code.waag.org/buildings/#52.2255,6.895,14) showing the age of buildings in the Netherlands. Choice of color scheme is obviously debatable from a cartographic point of view (why a diverging scheme instead of a sequential one, and why not center the diverging one's on a meaningful date, e.g. WW2?).
Want to do it better: Full source and instructions available (https://github.com/waagsociety/buildings).