So what's the best? Anything that stands out for Star Wars maps in particular? Free, paid, either?

Guess that really depends. How much work are you expecting from the software vs the end user. For the greatest power/flexibility you have Illustrator/Photoshop.

Or you can use something like Campaign Cartographer and make/find some custom symbol sets for Star Wars.

http://www.cartographersguild.com/mapping-elements/346-free-symbols-sets.html

or maybe play with something like MapTool

http://www.rptools.net/?page=maptool

I like Campaign Cartographer for the ease of editing maps. There is a steep learning curve to it. If you are willing to work though it, you will be able to maintain very nice maps. The ProFantasy forms would be able at answer questions.

I just use Photoshop. If you already know how to use it, you can get symbols from where ever.