A tiny entity framework written in Java. It's inspired by frameworks like Ash (hence the name) and Artemis. Ashley tries to be a high-performance entity framework without the use of black-magic and thus making the API easy and transparent to use.
Long story short: Ashley is awesome.
Entity systems are really cool and can help you write cleaner game code, avoiding the classic inheritance hierarchy hell. This article does a pretty good job at explaining the benefits of entity systems.
It's funny how strongly opinionated developers seem to feel towards entity systems. Some love them, some hate them. Have a read, experiment with Ashley and decide for yourself.
Expect more Ashley related articles soon!