Shuttle's XS36V is a tightly integrated and fanless mini barebone. Just add some memory and storage for a complete system.
"The D2700 is Intel's most powerful Atom to date. It has a clock frequency of 2.13GHz, supports HyperThreading, and is manufactured on 32nm process. Also on-board is a 640 MHz PowerVR SGX545 GPU. It's actually a valid desktop replacement in most offices, small businesses, schools, and silence aficionados. With a power consumption of only 16W in idle mode, the XS36V is also very energy efficient."