It really depends on your style, ability, and the amount of effort you want to put into a map!

If you look at the tools of most professional fantasy cartographers, you will find photoshop and illustrator as their top tools. The closest open source (and free) option to these are gimp and inkscape. These tools tend to need some artistic ability and experience to get decent looking results.

Programs like cc, fm and dj all have two huge advantages in that they are tailor made for producing maps, and they come with big sets of clip-art.

The best idea is to pick one that you are comfortable with, and explore it's capabilities fully. Remember, software doesn't make maps.... cartographers make maps

-Rob A>