I am a huge fan of YouTube. It is a great way to waste time on a rainy day or a great source of information. Youtube makes things as easy as they can be when searching for a video. All you need to do is type in what you are looking for and you will find a video. Off course there are usually more vidoes than you actually need, so using this in a middle school such as mine can be tricky and would probably need parental consent. As for using it as a coach or in the classroom it is a great tool. As a coach if I find a video about proper technique I want to share with my players I can easily share it with them. As for the classroom there are plenty of interesting videos that i show my students, especially if we don't have the materials to do a certain activity and still want them to see a lab. Whole lessons could even possibly be taugh using YouTube.
I selected this video of Tony Gwynn talking about hitting because this is one of the ways I would use Youtube as a coach.
The second video i selected is one that I would show in my science class.