Adafruit Industries Adafruit Industries PiUART - USB Console and Power Add-on for Raspberry Pi
Here's another super handy add-on for your Raspberry Pi computer, perfect for 'head-less' setups! The PiUART adds a MicroUSB to serial connection so you can use any serial port software to connect to the Pi's console. It plugs in and is fast and easy to add whenever you need to connect to your Pi. Two LEDs connect to RX and TX on the serial converter chip so you get blinking whenever data is sent or received.
Adafruit Industries PiUART - USB Console and Power Add-on for Raspberry Pi