The best way of downloading videos from Youtube is here. You can download all the flash embedded videos from almost any site with a click of a button. Yea, the flash videos are literally a click away.
After installing IDM, a "Download This Video" button pops up whenever you are watching a video anywhere in cyberspace (shown in the picture below). Just click on the button to start downloading clips. It's as simple as that; you do not have to separately launch Internet Download Manager. What's more, you can choose to download a clip at any point during the video, and the scene will be captured from the start. The download will proceed in the background even if you pause or stop watching. And you can download more than one video at the same time.
IDM will start downloading the video and show its standard download dialog. If the server has not specified the file name explicitly, IDM will name the file based on the web page title. You can also edit the filename, add a description, and change its path or category on this dialog.
As we stated you can download videos from almost any website.
You should have an FLV player (or codec or video converter) installed to play FLV videos. You can get more information about FLV player here.