I also found this thing called download helper its a firefox 2 plugin that can also download youtube videos
also when you are on a page containing links to images or movies, you can download some or all of them at once. Moving the mouse over the items in the menu will highlights the links directly in the page to make sure they are the ones you want to pick up.
DownloadHelper also allows you to download files one by one, so that you keep bandwidth to surf for other stuff to download.
i have it and it works pretty well
https://addons. mozilla. org/en-US/firefox/addon/3006