an ATTiny45 microcontroller, and a couple of passive elements can get you the USB circuitry for under $5 - e.g. http://stuffthingsandjunk.blogspot.com/2009/06/a

an ATTiny45 microcontroller, and a couple of passive elements can get you the USB circuitry for under $5 - e.g. http://stuffthingsandjunk.blogspot.com/2009/06/attiny45-usb-key.html http://stuffthingsandjunk.blogspot.com/2009/06/attiny45-usb-... I've used the V-USB library in a couple of fun projects - it's nothing short of awesome.