The image on the right shows a box made out of 6 business cards. These boxes can be easily made in a couple of minutes (once you have made the first one).
They are a great way to amuse people and there is almost always someone in reach who has some spare business cards. These cubes are based on the design from Ned Batchelder.
The first step is to fold 6 cards in the following way. Place one card on top of another in the shape of a cross and then fold the overhanging parts over the other card.
The next step it to place these 6 cards together so they all hold themselves in a box shape. You can tell if you have done it correctly because you can throw the box in the air and then catch it in one piece.
If you cut a notch out of the edge of the cards you can make a square with a corner cut off that you can balance it on a corner.
If you fold in the notch you can make also balance the cube.
If you fold in all the corners you come up with something like a ball. You can make a larger ball by joining together squares and triangles.