Java Library for Android

http://randomdotnext.com/retrofit-rxjava/
http://blog.danlew.net/2014/09/15/grokking-rxjava-part-1/

Image Loading

http://square.github.io/picasso/

https://github.com/nostra13/Android-Universal-Image-Loader

http://droidparts.org/image_fetcher.html

https://github.com/koush/ion