4. Boulder, Colo.
Percentage of bicycle commuters:
Now we're getting into the heavy hitters -- towns where one in 10 people or more take their bike to work. To the University of Colorado students who make up 35% of the city's population, the biotech, aeronautic and defense company workers who bike through their commute and the two-wheeled travelers who help keep the city delightfully weird, the bike is the way to go in Boulder.
The city has more than 300 miles of trails, dozens of bike underpasses that speed riders past busy streets and a government-funded site, GoBoulderBike.net, that helps cyclists find the shortest route to their destination by bicycle, how many calories they'll burn along the way and how much they're saving in gas money by not driving. The overwhelming majority of the city's streets have bike lanes or easy bike access.
Boulder also sponsors a walk-and-bike month each June that includes free bike clinics, rides, tours, repair workshops and even happy hour drinks for riders. The city's efforts also get a lot of help by local bike groups, including the nonprofit Community Cycles, which hosts bike-in movies, bike collection drives, bike-trail opening events, bike workshops and clinics and "earn-a-bike" programs that allow Boulder residents to pay for a bike by working hours in the group's shop.
The most inherently boulder bike events, however, are the Thursday cruiser bike rides that feature custom bikes decorated with lawn ornaments, picnic tables or whatever the groups hosting the rides feel like adding to them and costumes that can range in theme from fuzzy Santa costumes for Christmas in July to random video game characters. The theme changes each week based by the organizers' discretion, with this summer's Thursday motifs including cops and robbers, historical figures, steampunk and heavy metal. The bikes and the "Happy Thursday" greeting yelled by the cyclists are the only constants in an event that's consistently odd and quintessentially Boulder.