Neatorama reader Aubrey introduced us to the Chiditarod. It is the urban equivalent of the Iditarod, except instead of dogs and sleds, it's dawgs (humans) and shopping carts.
This year's race, held on March 1, 2008, was done for the charity Burners Without Borders:
When I first arrived, I saw what appeared to be a logistical nightmare unfolding before my eyes. Vikings, Pirates (a lot of Vikings and Pirates), Pac-men, Knights of Camelot, Baseball Furies, Mario Brothers, Where the Wild Things Are, Pilots, and Ninjas among others. 83 teams consisting of an average of 3 to 5 people each in costumes ranging from utilitarian to elaborately awkward trying to squeeze onto a small lot covered with ice and mud.
http://www.ninetyninetyfour.org/2008/03/chiditarod.html - Thanks Aubrey!