Spirited Away is one of those apps that hides unused apps after a while. Did I say “is one of those”? If you keep searching you won’t find many, so Spirited Away pretty much became the standard for uncluttering and get concentrated apps.
With [Houdini] we have one promising new candidate for this kind of functionality. The app looks good and has a couple of nice settings.

Despite the author claiming the app is ugly, it’s quite useful. Check it out.