There are several ways to download movies from Youtube and other sites. In
Firefox you can add 1-Click Youtube Video Downloader or Video
Downloadhelper. There are similar utilities for Chrome or Chromium. Another
way is to go to /tmp in the root file system and when the video has finished
downloading you can drag the temporary file to your desktop and rename it.
You can right-click on the file and go to Properties and you can actually
watch the file size increase as it loads. The file name will look like this:
FlashIUo0e9 and the icon will be for a video.