FlyingPiMonster has developed a WYSIWYG text editor, usable inside Minecraft! Wait, what does that even mean?
WYSIWYG is an acronym for "what you see is what you get," a style of editor that shows what will be displayed in the final post, work, or product. In this case, the editor is useful for its convenience in the game - run through command blocks, players could create any number of interesting text effects and arrangements for custom signs, scoreboards, and quite a lot more besides. While many text editors can produce this sort of final result, very few of them are as easy to use, or clear to understand.
Interested in giving it a go? Check out the JSON Text Editor thread!