Other World Mapper. It simply does what it says it can do and the learning curve is small.
I've tried to use many versions of Campaign Cartographer and it is simply way beyond my ability to understand. It's not that I do poor maps with it, I just can't do ANY maps with it.
Hexographer is great for hex maps. It does what it says it will do. I'm looking for a different look with the map I'm currently toying with, but I'd certainly use Hexographer again.
Those are the ones I have the most experience with.
Of course, this question is asking about outdoor and setting maps, but what do you use for your dungeon maps? I know I can do them with Other World Mapper, but options and ideas are always a great thing.