Please remove if not allowed.
Perhaps some of you here are able to recommend me good tools and sources for map creation? I am looking specifically for those which allow creation of fictional and creative maps (cities, towns, lands, continents, the whole globe).
Please do not recommend Azgaar or Watabou since I am already familiar with them!
Videos
Azgaar's Fantasy Map Generator is probably the best (free) map generation tool available.
It's not perfect and it can take quite a bit of playing around with to get the results you want but it is miles ahead of most of the other generators around.
That being said it makes typical spherical worlds. It should be possible to use it to make a discworld but you'd have to take the output and modify it to suit your needs, whether through using some kind of projection or just cutting a circle out of the generated map and calling it your world.
Take a look at the Sid Meier's Civilization game series, now on number 6.
It generates game maps randomly with configurable parameters that may or may not allow matching your choices.
It's round, but projected into a rectangle, so should be easily adaptable to a ring.
It's usually output into a new game under a lot of fog of war, but look into the modding scene, there may be a fast way to see the whole of it.