The sport of the uber leet. You scan for wi-fi networks on your laptop whilst driving around, sitting in mall parking lots, outside the hot chick you have your eye on's house, etc.
Some popular programs war drivers use are:
Wardrive ToolBox: http://www.xenon-inc.com
Just remember, it may be illegal to use a wireless access point without permission from the owner.
You should see these nudies I collected from last night's war driving.
Prices shown in USD.