WarChalking is the practice of making chalk marks on buildings or pavement describing a nearby WLAN AccessPoint. The networks are most often found whilst WarDriving or WarWalking. The symbols resembles somewhat those used by hobos during the Great Depression in the 30s. It started in the late summer of 2002 and got much media attention, but during the winter it seems like most people dismissed it and forgot all about it (heavily disputed by the people of the warchalking homepage).
People tend to argue if this is
Read more about it at the 
official homepage.
One page links to WarChalking:
