Saw a video that you liked on Youtube.com and you want to download a copy for your own keeping? Check out this web site http://www.keepvid.com that let you do so for free and there is no need to install any special software or plug in on your own computer.
This site also allows you to download videos from many other popular web sites.
This is one of the easiest way to extract videos from other video sharing web sites!
Hope you like it!