Good morning, everyone!
I see that some of you were talking about Scrivener. I was looking for a software like that and tried it out. It has so many features that it confused me so much. I toyed with it for a few hours before I just gave up. I settled for Storyist (Mac-only as far as I know) and it's very simplified, but organized. You can use it to actually write the story, plan the story, or both. If you want to get straight to the point, everything has its place.
I've been using it for a few months now and it has really made a difference in my planning. I am a planning whore. Before, I would just use notebooks or Microsoft document with trillions of bullet points for my planning. If I don't plan then my story goes all over the place. I haven't written in the program yet, but I think I will start with my shiny new idea, Dead Moon.
So if you got a Mac, you should check out Storyist. I recommend it. It takes a little while to get used to, but I personally love it.