Designed for iPhone 3G and iPhone 3GS, the new Bandshell - http://www.bandshellcase.com/ - is unique among the pantheon of cases. The affordably-priced unit (U$19.99) is constructed of impact-resistant polymer and comes in twelve pleasing colours.
Like many cases, it's ultra-slim and durable, but what makes it stand out from the crowd is its additional functionality. Besides providing protection, it amplifies volume and improves sound quality. And it does it all without the need for addon speakers and cords. A further bonus is that it serves as a helpful viewing stand which eliminates the need to hold the iPhone, or lean it up against something like a pile of books or a shelf. Fashionistas will have fun customizing the apt-named Bandshell by switching out the sound door from one case with another.
Special Note: Bandshell is participating in "Free Shipping Day" (December 17, 2009), check - http://www.freeshippingday.com/ - for details.