Some even come with a keyboard.
Clockwise, from top left: The Ben NanoNote runs its own custom build of OpenWrt, the Jlime distribution or anything else you can get to run on its 336MHz MIPS processor. Only 1,500 pre-manufactured units were made, but the hardware design is available as an open project.
Next up in size, the OpenPandora (starting at $479), is billed as a mixture of PC and gaming console and is only a little larger than the Nintendo DS.
The Gecko Surfboard ($119) packs an Intel-powered system into a standard-sized keyboard but only uses 5 watts -- hearkening back to the everything-in-the-keyboard design of the Commodore 64/128.