Finally, a Google has put together a user interface style guide for Android. Better late than never.
“It’s not enough to make an app that is easy to use. Android apps empower people to try new things and to use apps in inventive new ways. Android lets people combine applications into new workflows through multitasking, notifications, and sharing across apps. At the same time, your app should feel personal, giving people access to superb technology with clarity and grace.”
Link: Android Design (android.com)