incredibly small linux computer

This may sound strange, but i need to make a very small linux computer with all of the following. -3 usb plugs -a battery powered power supply (like a laptop) -enough power to run damn small linux it doesn't need a hard drive, (a flash drive will do) and it doesn't need any form of permanent input or output. it just needs to be able to boot up and run a few programs. i also need to be able to carry it easily (hence the small). so what should i be looking at here in terms of motherboards and the like? EDIT: why doesn't this forum keep my formatting?

i'm literally looking to make it as small as i possibly can. i mean, it would be killer if i could get it all in something about the size of an ipod. the bottom line is, i need to be able to carry it around comfortably. (while it is running). that sheevaplug thing is the perfect size but... i need it to run on a battery. so no go.