There is a saying, "The map is not the territory". While there are many reasons why this is true, there is one aspect regarding maps of the whole Earth that caught my interest quite a while ago. The Earth is more or less a sphere, how do you project a sphere on a plane? By distorting it, of course. Knowing that maps are distorted projections is one thing, getting a feel for that distortion is another.
If you could animate a map by continously changing the projection point, you could get a better understanding in which ways and to what extent different areas of the map are distorted. A few weeks ago I just realized that the individual frames of such an animation could be generated by xplanet and then an animation can be created by joining together all these frames. Since you don't want to manually generate all the frames you would need a way to automate the whole process. I wrote a short Python script that generates the frames by calling xplanet in a loop and then creates an avi animation using mplayer.