I really enjoy the mapmaking process of worldbuilding. Especially when I’m feeling blocked in the process of writing, opening up Photoshop and doing some map work is a good way to get the juices flowing. Or at least spend the time somewhat productively.
Lately I’ve been building maps for my space opera setting. My challenge of late has been making a map that is really of 3-dimensional space (as a star map would have to be) on my 2-dimensional display. As I’ve mentioned before, ChView is an excellent resource for making a manipulatable 3-D starmap… except for it’s not designed for showing political boundaries. I want to be able to glance at a screen and see how territories are carved up. 
One big challenge in turning the 3-D map into a 2-D depiction is, of course, that loss of dimension. Here’s a small sample:
This is a section of space that is, on the X&Y plane, near Earth. See it up there, listed as “Terra (0)”? The (0), of course, represents its Z-coordinate.
Now, everything here looks pretty close to Earth (in interstellar terms, that is, this is the nearby neighborhood.) But there’s one bit that’s pretty deceptive. “Eeio” looks, at a glance, to be just almost as close to Earth as Indus or Cygnus 1. But it’s not, of course, as it’s 63.45 light years away on the Z-plane. It’s pretty far away… but in our 2-D representation, it’s right there.
So I’m still working on figuring out a good way to show that visually, besides the Z-coordinate marker. We’ll see what I work out.