Scrivener - Scrivener is a content-generation tool for composing and structuring documents.
Plottr - The #1 rated visual book planning and series bible software for professional and aspiring writers.
Celtx - Celtx is a scriptwriting software platform with applications in a wide range of mediums but that specializes in helping screenwriters.
Plot Factory - Online story planner, organizer, and writing application.
Trelby - The free, multiplatform, feature-rich screenwriting program!
Story Planner for Writers - A beautiful and easy-to-use app to outline your novels and screenplays.