The Easter Egg Plotter by Andreas Dreier is probably one of the coolest NXT robots I’ve seen. Here’s a video (5mb) of the robot in action as it mimics the old school vector graphics printing devices. Unfortunately, only the different photo angles and captions are available to tell us about this creation.  It is clear, however, that one motor rotates the spool while the other two motors control the X and Y positions of the pen.  I would love to see the source code!

Andreas is also responsible for creating nxtRICredit - a tool enabling the creation of graphics for display on the NXT LCD.