I have a new favorite holiday.
The Portland Urban Iditarod involves costumes, beer, rain, Portland bridges, people who like to have fun, outdoor sprints, and all kinds of other awesomeness.
It's basically exactly what it sounds like: a team of people pull a stolen shopping cart around as if it is a sled in the Alaskan tundra. Except it's in the streets of one of the weirder cities in the US. And it's a pub crawl.
2009 Portland Urban Iditarod - Highlights from brewcaster on Vimeo.
I recommend starting one in a city near you.