As reported on World Naked Bike Ride sets attendance record | ksdk.com:
The sixth annual World Naked Bike Ride drew record crowds Saturday, despite the cooler temperature.
Approximately 1,800 cyclists in various stages of dress and undress pedaled 13 miles to protest oil dependency, raise awareness of cyclist rights, and to promote positive body images.
More on the site itself (link at the top). And yes, this is a bit dated, but still I thought it worth mentioning!