Download videos from YouTube.com

youtube-dl is a script to download videos from youtube
To install this script, type as root
#wget http://youtube-dl.org/downloads/2013.08.09/youtube-dl -O /usr/local/bin/youtube-dl
#chmod a+x /usr/local/bin/youtube-dl
and to update it

#youtube-dl --update

To download videos, just type youtube-dl and link direction, for example

$youtube-dl http://www.youtube.com/watch?v=hUYzQaCCt2o

Also you can use this script to extract the audio of theses vidios, for example

$youtube-dl --extract-audio --audio-format=mp3 -t http://www.youtube.com/watch?v=hUYzQaCCt2o

Source: http://rg3.github.com/youtube-dl/