This library focus on giving tour about your application and its features. You can highlight the where to tap to enable or disable the feature.
AppIntro is an Android Library that helps you make a cool intro for your app, like the ones in Google apps.
Since Google introduced the Material design philosophy I have seen quite a few apps with a nice clean, flat showcase view (the Youtube app is a good example).
A super easy-to-use page indicator for the Android Support Library v4's ViewPager widget with Material Design ink animations.