Recently I have been experimenting at building video tutorials. I have worked to build these for MindManager and Dragon Naturally Speaking and several other tools.
There seems to be a large market for this type of service for professionals looking for quick solutions, but there is an even bigger market for it for schools hosting distance learning degree programs. Capella University recently put out a release about one of their professors books that highlights the need for positive feedback in learning environments.
That is a key element but the first element of that is feedback. A student or person seeking knowledge can get a great deal of information from text but they can get even more from audio and far far more from video tutorials. The more points of stimulation a person can receive the more they are likely to absorb, understand and retain that information.
Ideally, the information they absorb, retain and understand will be able to be synthesized into their ability to use that knowledge and information to increase their productivity. This puts a premium on the ability to put out video tutorial or teach by example services online.