I use an IVAR side panel from IKEA. Lean it agains a wall at a slight angle and throw clothes over the horizontal bars. Done.

Stands almost entirely flat against the wall if you don't use it, comes in different sizes, is cheap and most people who have seen it in my room thought it looked kinda cool.

If you truly want to hide it, this usually fits behind a door pretty well.

[![IVAR][1]][1]


  [1]: https://i.sstatic.net/ykA7x.jpg