How to program a AVR (arduino) with another arduino

Step 6 Burning the Arduino bootloader

Connecting
I cheated a bit cause i used a RBBB to simplify the connections. The schema is on picture #2.
If you use 2 arduinos use the picture #3 and connect the ISP pin to the ICSP 2x3header on the second(slave) arduino.Only connect the usb power to the first board.

The GUI way
This is a little tricky cause you can't just use Tools-> Burn Bootloader -> w/ AVR ISP cause the default speed is too big for mega-isp.
Find avrdude.conf that comes with arduino IDE  (in arduino/hardware/tools/avrdude.conf) and change the boundrate for avrisp programmer from 115200 to 19200 (around line 312 )
Find and change in avrdude.conf 
programmer
  id    = "avrisp";
  desc  = "Atmel AVR ISP";
  baudrate = 115200;    # default is 115200
  type  = stk500;
;
to:
programmer
  id    = "avrisp";
  desc  = "Atmel AVR ISP";
  baudrate = 19200;    # default is 115200
  type  = stk500;
;
Now you can use Tools-> Burn Bootloader -> w/ AVR ISP (after you select the proper board from the Tools menu)

Commanline
You can also use the commandline:
Edit arduino/hardware/bootloaders/atmega/Makefile
and change ISPTOOL/PORT/SPEED to:
# enter the parameters for the avrdude isp tool
ISPTOOL    = avrisp
ISPPORT    = /dev/ttyUSB0
ISPSPEED   = -b 19200

no you can write
$ make diecimila_isp
to burn fuses and the bootloader.

Test
Now connect you new arduino to usb and burn the blinky!