Arduino as USB to Serial Converter

Ground the reset pin in order to bypass the Atmel chip.

Upload Arduino code that denotes RX and TX pins as INPUTs, so that the Atmel chip does not interfere with the onboard FTDI chip. Example:

void setup()
{
  pinMode(0,INPUT);
  pinMode(1,INPUT);
}
void loop()
{

}

source: https://web.archive.org/web/20110207183541/http://students.sabanciuniv.edu/kehribar/?p=19