The Beagle boards are open source, fanless, low cost (a beagle bone costs $89) computers that can run different OSs such as línux, and Android. They come stripped from peripherals, which makes them great for personal customization. They come in three flavours, the beagle bone, the beagle board and the beagle board XM.
More details and registered projects (for several examples of what these boards can be turned into) can be found at http://beagleboard.org.
Also there are nice tutorial videos on how to get started with the beagle bone: