Fanout sounds wonderful. Massimo's blog has a post on using the Arduino as an AVR-ISP (http://tinker.it/now/2007/02/19/make-an-arduino-ng-into-an-avr-isp-programmer-for-good/
), but it requires changing the crystal on the board. It would be great to have a way to use an unmodified Arduino as an AVR-ISP. If you got that working, I'd be very happy (and so would many other people). STK500 would be the ideal protocol for talking to the programmer, since it's what the current bootloaders use, but anything supported by uisp/avrdude would be fine.