Youtube-dl: Download Videos from the Command Line

Try youtube-dl to download videos to hard drive and watch them later when not connected. It uses the MIT licence. Youtube-dl is a command line tool and thus has to be run from the terminal.
Enter youtube-dl, the -t switch, the username and password for your account, and then the URL of the resource you wish to download which you can get from your browser's location bar, like this:

youtube-dl -t -u username -p password http://www.youtube.com/watch?v=Y2S9rwyQkJE

The -t switch means use the title of the video we're downloading. Enter 'man youtube-dl' for more options.  The application also prints the size of the video and the estimated time it will take, the ETA, to the terminal. Wait for it to finish and enjoy.