During its Winter Seat Giveaway, Megabus.com
offers free bus rides
via coupon code "WOW200K". That's the best deal we've seen from this service. It's valid for all routes and travel between January 12 and March 1. Bus stops are located in 31 cities including Washington D.C., Ann Arbor, Chicago, Cincinnati, Cleveland, Columbus, Detroit, Indianapolis, Kansas City, Milwaukee, Minneapolis, New York, Philadelphia, St. Louis, and more. Deal ends after 200,000 coupon redemptions.
Update: Megabus.com is currently down.