From a company that sells Raspberry Pi’s in North America comes this:

One of our top selling accessories for the Raspberry Pi is the case. Cases for the Pi come in a multitude of styles, sizes and colors, but if you’re like us, you’re the type of person who loves to build it yourself. Today we’re going to build a bare-bones case out of cardboard with supplies you may already have laying around the house.

Read the rest of the article here:
Build Your Own Raspberry Pi Case from Cardboard or Cardstock (MCM Electronics)

In case you are wondering, the finished enclosure looks something like like this (depending on what you make it out of). Just be sure to use a non-conductive material: