Through July 14th you can score Free Cars 2 Movie Tickets (up to $7.50) from Walmart! Just start a Secret Mater Mission, send a decoded message to a friend and earn a ticket!
It seems like they are replishing the tickets at around X:38 of each hour. Just got then and keep refreshing until the message that all the tickets for this hour have been given away. Choose a friend to send a decoded message to and enter the capcha code. You should win a ticket on your first try...if you get a coloring page just immediately try again.
Limit 2 tickets per facebook account! Good luck! (FYI - I was able to score 4 free tickets very easily, but only one per hour).