Chockadoc is a place to find full-length documentaries that you can watch online for free. Chockadoc, like sites similar to it, pulls most of its content from YouTube. The benefit of using Chockadoc over YouTube is the categorization of the videos. The categorization makes it easier than searching YouTube to find documentaries about a particular topic or theme.
Applications for Education
I'm sure that for readers working in schools that block YouTube will not be able to view most of the content on Chockadoc. If that is the case for you and you really want to use a video that you find through Chockadoc, you might want to consider using a tool like KeepVid to download the video at home then display it directly from your laptop. Bear in mind, that using KeepVid may be interpreted as a violation of YouTube's terms of service so use your discretion.