Give your collections (on any View at all) a fancier look by adding a cool way to check elements. If your list can multi-select elements, you can add this component as a "status indicator". This is basically a customizable view flipper, with a "front" and "rear" faces, and an "accept" image in the "rear" that will animate changes in its state, mostly like the GMail app.
A really simple library that help you to display a custom toast with many colors (for success, warning, danger, info, dark, light, primary, etc.), or with rounded corners, or event with image.
An Annotation based validation library for use with Android's DataBinding library in an MVVM architecture.