Viget Inspire, "an inspiring blog which discusses web design standards, trends and techniques", has an experiment on the uses of CSS3 box shadows.

The article shares 39 original uses of "box shadows" and it is a great showcase of what can be accomplished with this CSS3 property.

In order to create the effects, some examples have multiple box shadows and make use of other CSS properties like :before/:after, transition, webkit-keyframes, text-shadow and background-image: gradient.

39 Box Shadows