Cassiopedia offers free high definition science education videos . " While the videos are self- contained, they are embedded in a larger story intended to generate interest in the science." The videos can also be found in the Beyond Campus section of iTunes U.
This website is very easy to use. It does not require a sign up or any software download. Just head over to its main page. Click on the tab named 'videos' and start browsing its content. The videos are organized into different categories such as Biology, Space, Physics, Evolution,General Science and many more. Click on any video and you will be directed to a page where you can have more info about it such as its description, title, duration and a link for download.