ive used a fanless mini-itx as my home linux server for years. its fantastic. Via came out with the nano-itx, then the amazing pico-itx, and now the mobile-itx.
512MB of ram, runs linux. its pretty close to being able to build your own PDA/media player or maybe a cell phone. Cover the front side with a height-width matching touchscreen display and cover the backside with a li-ion battery.
i started this little googling-adventure looking at the Arduino project board. cough. 16mhz. 512Kbytes of flash. pass.