As some might know there are several FTDI chip based usb to serial converter breakout boards. Sparkfun produced several of them through time , and recently Adafruit launched a new product called  ”FTDI friend”. Those are the well known ones.  But if you have an Arduino board with usb connectivity ( like Duemilanove ) , you don’t need to buy any of those for basic usb to serial converting tasks. If you have a Seeeduino, you are luckier!