From the MAKE Flickr pool

Flickr member drug123’s MEGA-ISP shield turns an Arduino into an In-System Programmer for AVR Chips –

Prepared schematics and board layout of this Arduino shield during one-hour-long phone call. Spent another hour to create “physical interpretation”.
Purpose of this PCB is providing ISP header to turn Arduino in full-functional programmer for AVR microcontrollers.
Firmware to turn your Arduino board into ISP programmer can be found here.
Connected device could be seen here.
All components on PCB were scavenged from old dead LAN cards.
I have released schematics for improved version of this board under CC BY-NC-SA license, you may find it here.

This could prove quite helpful as a backup for my USBTiny – I’ll have to give it a go myself.

HOW TO – use Arduino as a high voltage programmer