Today marks the official start of the second round of the Pepsi iTunes Music Promotion. The first winning bottlecaps appeared in Los Angeles, CA last week but unredeemable until today. One in three caps of specially marked bottles of Pepsi, Diet Pepsi, Sierra Mist, and Mountain Dew contain a winning code redeemable at the iTunes Music Store for one free song. The full set of official contest rules can be found here.