If you’ve got a pile of bricked AVR parts sitting around, or have a penchant for inadvertently blowing the wrong fuses on your devices, then you might want to check out Jeff Keyzer’s HV Rescue Shield. The basic idea is that there are certain blocks of memory (fuses) on the microcontroller that control how it starts up, which can’t be erased by a standard programmer. Instead, you need a device capable of
generating a high enough voltage to clear them generating a high-voltage signal to put the chip into a special programming mode, so that they can safely be re-programmed to correct vales.
Jeff’s solution was to create an shield for the Arduino, which has a builtin DC-DC converter that generates the 12V signal necessary to reprogram AVR chips. The whole project is open source, and schematic and code can be found at the project website.