Problem: I teach classes where we build amsat antennas and try to listen to satellites and the International Space Station. It is really hard to point to nothing at all, so I thought this would help (at least, during the night). It also has the handy dandy feature that it can be used to point out astronomical items if you modify the pyephem script barely (I'll include another program to run for this I think).
This thing points things out to you using a laser pointer in the night. It should probably never be used unattended unless you want the police to come by because you shone a light right into an airplane on approach.
It was designed to run on a pi but can also run on a laptop etc. It runs a python script which loads a TLE located in TLE.txt in the same and sends alt+az commands through the serial port to the arduino. The arduino decodes the alt+az and commands the servo and stepper accordingly. I implemented a horrible motion algorithm for the servo because it was really shaking my laser all over, but the stepper is just linear motion so there is room for improvement.
Video here: https://youtu.be/uu8M_wjfsk4