Sony has teamed up with Taco Bell with "Unlock the Box" promotion has a code to enter to win a PS Vita every fifteen minutes from January 26 through March 11. All you have to do is buy a "$5 buck box" at any Taco Bell and enter your code online. Winners will get a PS Vita 3G/WiFi, Little Deviants, a 4GB memory card and a choice of either ModNation Racers: Road Trip, MLB 12 Th Show or LittleBigPlanet.
If buying and downing a 1270 calorie box of heart attack isn't your cup of tea, you have two other options to win. Taco Bell has a mobile app called Reality Fighters Dojo where you can "battle" others for a chance to win. Also Taco Bell has a photo/video submission telling everyone what you are willing to do for a Vita, which will be voted on by viewers.
source: PlayStation Blog