How can I convert youtube vidoes to my iPod Shuffle for free? PLZ HELP?

i hav a ipod shuffle and i want to put some of my fav. youtube and/or other popular vid. website's songs on it

if u know any websites and downloads for free and w/o big risks tht will harm my computer. Which will convert youtube vids. and/or other vids to my ipod shuffle plz tell me ^^

also since i hav a ipod shuffle i hav to make the music vid. into just the music… o.O ^^ so plz help me on tht too! =]

thnks for reading n answering ^^