You can convert YouTube movies onto your iPod video with a free program like iTube:
iTube is an easy to use Windows program that will enable you to transfer any YouTube video onto your iPod video.
Simply enter in the YouTube page URL and iTube will download the file, convert it, and then import it directly into iTunes. The next time you plug in your iPod video it will automatically transfer. If you don't have an iPod video, you can still watch the movie in iTunes.