Arduino-based AVR High Voltage Programmer
It turns out that when you flash the RSTDISBL fuse on an AVR microcontroller, you lose the ability to program the chip with SPI and flash it back again. Rather than throw away the chip, I made this Arduino-based programmer that uses the less common High Voltage Parallel Programming Mode of the AVR to fix the fuses. Now I'm back in business with a working AVR again!
Code and schematics are available here:
By the way, that is an Arduino NG on the bottom, but this should work for the newer Diecimila as well.
Update: I've developed a kit based on this design, which includes an awesome custom PCB and is totally open source. You can learn more by visiting my blog at mightyohm.com.