This is a proof-of-concept dual bootloader for Atmel AVR atmega chips. It combines a serial bootloader and a mmc/sd card based one in the same 2kb of flash memory that is normally used by the arduino serial loader alone.
You might ask Why? Well, I have quite a few arduino “in the field”. I can simply drag a .hex file to an SD card, insert it in an SD shield, and field-upgrade my boards without additional hardware. At the same time, I can connect the serial port and start developping with the normal Arduino IDE.