Check out these full computers built into old radio bodies.
Each one is custom made but tend to have relatively similar specs. They start with Ubuntu Linux, so they’d make a solid media server, but other operating systems can be installed. “The system boasts an Intel BOXD945GCLF2 Atom 330 Intel 945GC Mini ITX Motherboard, 2 GB RAM , 250 GB SATA 7200 rpm Seagate HD, DVD-RW (with LightScribe), and Gigabit Ethernet.”
Photo of the back of the unit after the jump.
The same person has also started working the Chumby (an internet connected device) into the same form factor.