This insane David Belle/Parkour video (WMV 4.7MB, hosted by this fellow) crossed my aggregator this morning. You have to get a bit into it for the death-defying stuff. A quick Googling of "Parkour" turns up a ton, including parkour.com, Le Parkour, and Urban Freeflow. All provide links to a pile of videos. Post if you find any that are particularly cool. I like the Nike "Angry Chicken" commercial (WMV 1.2MB, found here).