AdaFruit makes a handy Serial to USB adapter called the FTDI Friend. This lets you connect your laptop or computer to a digital level serial port on a Raspberry Pi or Beaglebone using the FTDI serial drivers. I use these when talking to evaluation boards and what not but there isn't an easy way to hold them in place if you don't have an FTDI compatible header on the board so this holder can be glued down to my plastic proto area (like my Standoffs or PowerJack) and it doesn't move around. Its scaled to print on my Replicator 1/Dual you may need to tweak the width if the fit isn't friction tight. This is pretty straight forward, although it does depend on your printers X accuracy. The board should slide in with some friction so you won't pull it out by plugging in or unplugging USB, but not so tight that the plastic distorts. My calipers say the gap should be 17.75mm wide for the board, but I printed it at 18.25 to get it to fit. In one of the pictures I show it in use, the bottom is attached to my Panavise circuit board holder with some double-sticky-back foam tape. I use Simplify3D to print it rather than the Makerbot Desktop though.