The right hand margin on YouTube can be a laden with "related" videos that you don't want to display to students when you use a YouTube video in your classroom. Here are some tools you can use to display YouTube videos without displaying the sidebar advertisements and related videos.
View Pure is a simple little tool that strips way all of the distractions of related videos, comments, and promoted videos. To use View Pure just copy the link of a video into the "purifier," click purify, and your video will be displayed on a blank white background. You can also install the View Pure bookmarklet to accomplish the same goal.
Quietube is a handy little browser extension that removes all the clutter from YouTube allowing you to view only your selected video. Quietube removes all advertising, sidebar content, comments, and ratings. Installing Quietube requires nothing more than dragging the Quietube button to your toolbard. Then anytime that you're on YouTube click the Quietube button to remove all of the clutter and just watch your selected video. Quietube works for Viddler and Vimeo videos too.
SafeShare.tv makes it possible to view YouTube videos without displaying the related videos and associated comments. To use SafeShare.tv simply copy the url of a YouTube video and paste it into SafeShare.tv. SafeShare also offers browser bookmarklet that eliminates the need to copy and paste links.
VideoNotes is a neat tool for taking notes while watching videos. VideoNotes allows you to load any YouTube video on the left side of your screen and on the right side of the screen VideoNotes gives you a notepad to type on. VideoNotes integrates with your Google Drive account. By integrating with Google Drive VideoNotes allows you to share your notes and collaborate on your notes just as you can do with a Google Document.