Here at ScreencastLearning.com you can view instructional videos on a variety of topics. You can even become an instructor and upload your own screencasts to be enjoyed.
For most users learning anything about an operating system, a piece of software, or a website is best done by watching someone do it right. Going through steps in a book can often get tedious and confusing. With a screencast you can watch and learn at your own pace. Going back over a certain topic is no problem, just drag the slider back to that part of the video and watch it again!