I would like to create ten or fifteen minute podcasts with video
(vidcasts). What the viewer/receiver will experience, is a window on
their screen that shows information being written, as if on an
eraseboard or blackboard  - they see just the information/text being
written, not the person doing the writing - with accompanying
step-by-step vocal instructions. Just to make this a bit clearer, I am
not looking for a way to show video of someone writing on a board -
just the information being written on a virtual board.

I need advice on which software or set of software will let me do
this. I have seen video tutorials that were made with Macromedia
Director, but I don't think that something made that way would be
suitable for a podcast/vidcast. I have been told that Flash can do
something like what I want, but I would like other opinions.