Yes, i know a very quick and easy way to take mp3 files out of a youtube video. All you need is an email.
Go to
www.zamzar.com
Then on the website where is says step one, click where it says url.
Copy and paste the url of the youtube video you want to extract the audio from and paste it in the open space for a link. (BE CAREFUL: make sure you delete the "http://" that is already there because you don't want it to look like "http://http://www.youtube.com/watch?v=7fSFWCY0uxE")
Then where it says step 2, choose mp3, which is a bit more than halfway down the list.
For step 3, enter your email address like it says to.
Then in step 4 click convert and when the window pops up click OK.
Once you get the email go under the blue box where it says "Alternatively click on the following link to download a copy of your converted file:" and click on the link below which should take you to another window.
After you click download in the new window it will download it and it should start playing on itunes or at least will be downloaded onto your computer.