Follow any of your favorite MLS teams on foursquare and then check-in to one of their games this season and you will receive a special badge and message.
All of the MLS stadiums on foursquare are conveniently listed here.
Each team has a different badge and message. Pictured is the New England Revolution badge and here is their unlock message:
Thanks for supporting the Revolution! How’d you like a FREE Revs T-shirt? If you’re at Gillette Stadium, show this badge at the Revs table on the main concourse above section 107. (while supplies last)
Good luck and GO Revs!