OrcBoard.org is the home for the open-source embedded controller, the uOrc. The uOrc provides interfaces to the "real world" devices like motors and sensors, allowing conventional computers and laptops to control robots, industrial automation machines, and more. The uOrc is completely open source, including hardware design, firmware software, and user libraries. In low quantities, the uOrc can be manufactured for around $150 per board.
Information for older Orc hardware is still available on the OldHardware page.