The useful_dir is useful code that may come useful for other developers. There will be different projects that are being commited into this directory in languages such as PHP, JavaScript, jQuery, HTML, CSS, HTML5, CSS3 and many more languages.
The first useful directory commited is Indigo. This contains files which are for a system that makes notes. As developers paper can become a nuisance. Just connect your localised database either on your local enviorment or your web server and it will save notes. There will be updates to this code for upkeep.