Storyist - A powerful writing environment for novelists and screenwriters.
Scrivener - Scrivener is a content-generation tool for composing and structuring documents.
Celtx - Celtx is a scriptwriting software platform with applications in a wide range of mediums but that specializes in helping screenwriters.
iA Writer - Minimal Design, Maximum Focus
Trelby - The free, multiplatform, feature-rich screenwriting program!
Dictation - The fastest and most accurate speech recognition software