Turning an Arduino of virtually any sort into a simple AVR 6-pin ISP programmer is old hat. But when Atmel came out with a series of really tiny AVR chips, the ATtiny10 and friends with only six pins ...
This is a fork of the code and examples from "Make: AVR Programming" that I've addapted to work with the Arduino Uno R3 (I'm using the SMD variant, but it shouldn't matter which UNO R3 you're using).