There's also a rather creative way of using these as Greeting Cards or notes. Just write "Push in!" on the ring, then one word of your message on each little tail that appears when in "star" mode. Most people go a little crazy over it (Its so cute!)...

... If they start to really bug you, you can throw one at them with a new message: "Its just a stupid piece of paper, fool" (And it fits perfectly, too)

It should also be noted that my wonderful Origami book (The Origami Workshop, By Gay Merrill Gross, if you're interested) attributes this design to Robert Neale of Leeds, Massachusetts, and has this to say about the design:
This amazing model transforms from a ring into a star and back again. It can be used as a coaster, a napkin ring, a card or package decoration, or hanging decoration; as a ring it can be thrown like a Frisbee. For a successful model, it is very important that you fold very neatly. If the units are not folded accurately or are joined together in a sloppy manner, you will hinder the smooth sliding action of the finished model. The Magic Star is a good example of how its creator, Robert Neale, combines his interests in orgiami and magic.