ScreenCastoMatic digital storytelling tool that is easy to use. It is a web based screen recorder. It allows you to create an instruction session or an artefact in minutes. An example of a screen cast that I made and then loaded into Youtube was a Prezi I created with narration. Please look at UBC Education Library Instruction Report.
I have also used Comic Life (not free but you can register for a free trial) and VoiceThread.
I also liked this ERIC Document entitled Constructing Digital Stories.