Alternatively, http://www.hexographer.com/, It can be a bit more hit and miss, depending on what you're wanting, and I've yet to discover how to make it pretty, but it's certainly functional. Though I think it costs to get all the features, can't remember.
@Nemaisare I'm currently looking at the Github one and it's really cool how it can generate a decently complex map for you right away.
I don't know how to edit the terrains though. I want to start my map just small because I'm not worldbuilding an entire world right away from the start. I want to just delete and add the continents as I wish.
I'm not sure if you can do a small then build outward map with that one. You can do a less detailed whole world and then edit a small space to focus on and go from there, I think. Have not explored it fully yet.
There is a tutorial and wiki if you haven't found it yet.