VideoScribe - Make your own whiteboard video animations with Sparkol VideoScribe – award-winning video scribing app for PC, Mac and iPad. Free trial available.
Scrivener - Scrivener is a content-generation tool for composing and structuring documents.
TTS Sketch Maker - Create amazing whiteboard sketch videos with text-to-speech human-sounding voices in minutes!
Celtx - Celtx is a scriptwriting software platform with applications in a wide range of mediums but that specializes in helping screenwriters.
Doodly - Create your own doodle video in just 60 seconds
Trelby - The free, multiplatform, feature-rich screenwriting program!