San Francisco is set to host the first 'Walk to Work Day' in the nation on Friday.  Walk San Francisco says there will be a number "Walk to Work Day" hubs set up from 7:30 to 10 a.m. throughout the city for participants to pick up an "I'm walking to work today" sticker, free snacks, cups of coffee and to register for prizes  Mayor Ed Lee and several city Supervisors plan to participate in the program by walking to City Hall from one of the hubs.  A map of the hubs can be found at