I have been experimenting with creating videos like those created by Salman Khan of khanacademy.org. My primary desktop is Ubuntu Linux for all purposes but I keep an old HP Laptop handy for occasional MS Windows testing.
Here is how the khanacademy video lectures have been recorded. Salman Khan delivers his lectures by writing text and drawing images on his computer using a graphics software (which can be paint, photoshop, gimp etc.). He also narrates what he is doing. The graphics software is serving as a black board. His voice and desktop activity is recorded by a desktop activity recording software like CamStudio for Windows or recordmydesktop for Ubuntu Linux.
To write text on a graphics software (your black board) you can use a mouse but using a graphics tablet is a much more easier. I borrowed a Wacom‘s Graphire tablet from a friend and plugged its usb cable into my Ubuntu 10.04 laptop. To my amazement, it got configured instantly without requiring any sort of drivers or configuration.
On Windows, I installed and recorded a video with sound using a free screen capture software CamStudio. It created a video in .avi format which was uploaded to youtube and played without any issue.
On Ubuntu, I installed recordMyDesktop and gtk-recordMyDesktop using usual apt-get command. I was able to record my desktop activity without any troubled. Its output was .ogv media file. This was also accepted by youtube and played without any hitch.
I am also learning to use some simple video editing software to remove unnecessary parts from a recorded video, add some captions and other minor editing. Will share this too as soon as I get comfortable doing all this.