An Apple patent has recently surfaced for a dynamically changeable OLED keyboard. The keyboard would rely on OLEDs to provide the graphics on the key surfaces. The patent application also details how such a keyboard would be manufactured.

Apple's Abstract:
Methods and apparatus, including computer program products, implementing and using techniques for providing a computer peripheral including one or more keys. Each key has several light emitting diodes disposed on a face of the key. Each of the light emitting diodes can switch on or off in response to a data signal received from an application specific integrated circuit dedicated to the key. A corresponding key and manufacturing method, as well as a computer system including one or more such keys are also described.

Apple's Description, in part:
Broadly speaking, the present invention provides methods and apparatus for dynamically altering the key faces of keyboard keys, such that they show an accurate representation of what action will occur when a particular key is depressed. In one embodiment the altering key faces are accomplished by placing a number of organic light emitting diodes (OLEDs) on each key face, and using an application specific integrated circuit (ASIC) placed inside each key to turn on and turn off the respective diodes. The respective ASICs are controlled by signals originating from the software application in which the user is currently working and by the selected language locale. As a result, the users always have current and accurate information in front of them about what will happen when a particular key is depressed on the keyboard, and there is no need to memorize what actions particular key depressions will cause.

In general, in one aspect, the invention provides methods and apparatus, including computer program products, implementing and using techniques for providing a computer peripheral including one or more keys. Each key has several light emitting diodes disposed on a face of the key. Each of the light emitting diodes can switch on or off in response to a data signal received from an application specific integrated circuit dedicated to the key.
Full patent here

Art.Lebedev has a new prototype keyboard called Optimus Tactus. The keyboard is one large OLED display, which is touch sensitive.