Screencasting is a digital recording of the images on a computer screen. There are several free applications which can be used to create a screencast.
Screencast Central - a collection of screencasts
Using Screencasting to engage your students
Use Screencasts to let students teach students
Applications in the classroom:
Create a screencast to show students how to open, create, save a file
Use screencasts to demonstrate the editing and revising process
Create tutorials using your activboard to model steps in a process