In a strange blend of "I don't know if I am mystified, horrified, or fascinated" I present
Cabspotting - the Cab Tracker. In essence, it's a realtime map of the cabs in San Francisco, tracking them. What makes it oddly compelling is the realtime nature and the paths the cabs leave as a trail.
Again, not sure where to "put" this, but good art should make you think. This did.