Want the students to watch a video from YouTube, but don’t want them to watch the ENTIRE video? Google Apps in action has wonderful directions on how to embed a YouTube video in a presentation so it will start and stop with the parts you want to watch.
The student can click and play any part of the video they want, but by default it will show what you want. So, don’t use this trick to skip over something that is inappropriate, because the student can really watch whatever they want. But, you can use this to help the student watch only the part you want them to watch.