First some Microchip Cities by Franco Recchia who has cleverly brought together these tiny components to create very appealing high-rise landscapes. More detail can be found in the Inhabitat article and further sources as always.
Now a beautifully crafted version of the London Underground Map made into a circuit board by Yuri Suzuki (a designer in residence at the Design Museum in London). Here you can see the finished piece but check out more in the DesignBoom post or the VIDEO.
[Yuri Suzuki circuit board map]
Lastly some clever landscape art using the PCBs as the layers in a contour model by Grace Grothaus.
[Grace Grothaus PCB art via her site]