Now that I read the category completely, I have to add: Riding on the City of New Orleans, by Arlo Guthrie.
Arlo Guthrie /City of New Orleans
http://www.youtube.com/watch?v=TvMS_ykiLiQ&feature=related
Great song. Made famous at Newport by Arlo Guthrie but written by Chicago's own genius, Steve Goodman, a good friend of John Prine who died too young.
You may also remember Goodman as one of the co-authors of "You Never Even Call Me By My Name."