Saving a flash movie or flash animation
Mozilla Firefox has built-in features to save Flash movies or animation or even games. When viewing a web page:
1. Right-click on the web page;
2. Select View Page Info;
3. Switch to the "Media" tab;
4. Select the Flash movie or animation or game (flv / swf file) you want to save;
5. Click Save As.
Just as simple as that.......
But this will work only if the flash or swf or flv file is cached. Else you might have to use some plugins. YouTube like sites wont cache the videos.
Best for youtube kind video download is to install downloader firefox plugin