I haven't posted my WIP in that thread, yet, but I've used a combination of Sketchbook, Gimp, and more recently,
Graphic, all with a Wacom Intuos drawing tablet.
I have kept an eye out for more dedicated software like
Jonathan Roberts'
Fantastic Mapper or
Other World Mapper. I would like to explore using something like
World Machine to create something more realistic, interactive, and versatile.
Edit:
I guess World Mapper is just about abandonware, supposedly
Terragen is currently the way to go.
Edit2:
I actually took up my mapmaking again last night and figured out how to overlay my map in google earth. This made me glad that I was using vectors, as it was a cinch to resize my map's dimensions and shuffle my continents around to achieve a more favorable position on the globe. It will also help for figuring out distances and climate.
The workflow for this is pretty nice, actually. GEarth just pulls the overlays from your file system (or a URL, I think), so if you overwrite the file (I export to tiff), it only requires a refresh to see the changes. I have a whole-globe wrap at the moment, but the resolution is limited, so if want higher rez zoomable features, I'll have to cut those out of the larger map and overlay them as separate chunks.
I'm not sure how far I'll go with this particular workflow beyond general positioning, however, as I'm wanting to make a proper heightmap and looking at tools like
Wilbur and
MapToGlobe.