In both my spare time and during work, I like to tinker with open datasets. One of these datasets is the BAG, which contains data about all the addresses and building in the Netherlands.
Back in 2013, I was inspired by the Waag Society and created the map shown down below, all with open source tools. In the meantime I have tinkered with the BAG trying to create nice polygons of postal codes, or finding all the relevant houses fit for renovation, based on the type of house, its age and orientation.
* roughly 290.000 euro for the whole of the Netherlands.