This Firefox add-on enables you to directly download videos from YouTube, Google, Metacafe, iFilm, Dailymotion and many other online video sites. It also supports downloading of all embedded objects on a webpage (movies, MP3s, Flash animations, QuickTime videos, etc.).
VideoDownloader adds a small non-intrusive icon to the right corner of the status bar, at the bottom of your Firefox window. All you need to do is click on that icon and download the video you are watching.
The extension works with more than 60 video sites, including Youtube, Google Video, iFilm, Metacafe, Dailymotion and a lot more.