Bookmarks

Java

Glide - Powerful and flexible library for loading, caching and displaying images
greenDAO - greenDAO is a light and fast ORM solution that maps objects to SQLite databases
Transitions-Everywhere - Backport of Android Transitions API for animations
Battery Historian - Analyze battery consumers using Android “bugreport” files
Facebook Rebound - Spring Animations for Android
Dagger - Dagger is a fully static, compile-time dependency injection framework for both Java and Android
RxJava
Retrofit - A type-safe HTTP client for Android and Java
OkHttp - An HTTP & HTTP/2 client for Android and Java applications
Butter Knife - Annotate fields with @BindView and a view ID for Butter Knife to find and automatically cast the corresponding view in your layout.
MPAndroidChart - Powerful & easy to use chart library for Android
Robolectric - Unit test framework

Android Source
Android Fragment onCreateView vs. onActivityCreated - An interesting conversation in the first answer follow reply.
Android Activity Life-Cycle for Professional Developers - Simpler and more complete than most of the resources out there (including the official documentation, unfortunately).

fullPage.js - To create fullscreen scrolling websites / single page websites
lunr.js - Simple full-text search
Trip.js - Help you customize a tutorial trip easily with more flexibilities
Moment.js - Parse, validate, manipulate, and display dates in JavaScript.
Underscore.js - It provides a whole mess of useful functional programming helpers without extending any built-in objects.

Bootstrap - HTML, CSS, and JS framework for developing responsive, mobile first projects on the web
Angular-Material - Implementation of Google’s Material Design Specification