variety of tools for watching YouTube videos without all of the "related" videos and advertisements appearing on screen. Watchkin is the latest tool in this market that I have tried. Watchkin is a service that allows you to watch and project YouTube videos without seeing the related sidebar content typically seen on YouTube.com.
Watchkin can be used in a few ways. You can enter the direct URL of a video into Watchkin to have the sidebar content removed. You can search for videos through Watchkin and have family-friendly results displayed (if a video appears that is not family-friendly Watchkin has a mechanism for flagging it as inappropriate). Watchkin also offers a browser bookmarklet tool that you can click while on YouTube.com to have the related content disappear from the page.
Applications for Education
The Watchkin website and browser bookmarklet are great tools for teachers who want to show a YouTube video in their classrooms without risking displaying "related" sidebar content. To be clear, Watchkin is not a work-around if your school blocks YouTube and it is not a tool for downloading YouTube videos. (Downloading YouTube videos is a violation of the YouTube terms of service).