Never thought I'd be excited about something so mundane as XML! I've just wrapped up writing a custom serializer and deserializer for our Level class as part of our game, Attraction. The coolest part about it was the schema file that basically defines objects within XML files. It's a powerful tool that let's you create elements, extensions, and wrap elements within other elements. I was able to tailor the schema to accept a level with any amount of entities, which included a set of components. It's all matched up to our entity system, Artemis.