Passbook is Apple's feature on iOS 6 that allows you to add gift cards, movie tickets, boarding passes, etc., all in one place. Many businesses have already integrated Passbook into their apps: Target, Fandango, Sephora, Delta Airlines, American Airlines. Today one major business added Passbook support, Starbucks.
The coffee company updated their iPhone app today for the long awaited feature. You can now add your Starbucks cards to Passbook and use them in stores.
The update also brings iOS 6 support, easier sign up for Rewards and many other improvements and fixes.
Starbucks for iPhone is free and available in the App Store [iTunes Link].