When I first saw the original project, I had the idea to build a tiny ISP programmer. In the and it got so tiny, that i added a hole, so it can be used as a key chain. The price per unit is around 5.4€.
It is based on the works found here:
v-usb from framework http://www.obdev.at/vusb/
usbtiny isp http://www.xs4all.nl/~dicks/avr/usbtiny/
vusbtiny http://www.simpleavr.com/avr/vusbtiny