An electro-graf is a graffiti piece or throw-up that uses conductive and magnetic paint to embed LED display electronics. An indoor and an outdoor electro-graf are currently being shown at Eyebeam.
As with the LED Throwies (see below), the potential applications of this technique are dizzying. The step-by-step guide to making your own is available at Instructables. You can also watch the video documentation on the Graffiti Research Labs site, and see a few examples in action at the GRL flickr pool.