Now that you have an idea of where to get yourself a skin, let's talk a little bit about styles of skins that you may encounter while shopping.
Full back only skins: These skins, as you have probably guessed cover only the shiny back of the phone.
Faceplate only skins: These are extremely rare, and usually must be custom ordered. They cover the front (except for the touch screen and home button) and wrap around about an inch of the back in one solid piece. They are difficult to apply evenly but still allow you to see any custom engraving on the back.
Full back and front plate skins: The most common type these models have a face plate on 1 piece and a full back plate coverage. Since they offer the most protection and design space, they are preferred by manufacturers of the skins.