I just started following HP Teacher Experience Exchange on Twitter and it is amazing!
They posted a video teaching how to create a story in a website called storyjumper.
To get access to this video go to: http://h30411.www3.hp.com/posts/1072386-VIDEO_Story_creation_tool_for_elementary_students?mcid=Twitter
This other tool is called Popplet:
It is worth watching and sharing.