I've been a fan of Platform.sh since it came out, even before I started at Commerce Guys. I'm a fan of using builder tools for constructing projects - Composer or Drush make (latter for Drupal) - instead of putting extra code into version control. However, this post is not about a PHP project, but one of my AngularJS projects.
A recent project of mine has been ContribKanban.com for the Drupal community. The name speaks for itself - it provides a way for contributors to work on Drupal.org project issues queues through a kanban board. This app has two purposes: visualize the Drupal.org project issue queues in a useful fashion, and provide an experiment that tries to fully utilize Drupal.org APIs.