Find a video on YouTube, then type the word kick, kiss, save or keep in front of YouTube and you will be directed to the Save YouTube or KeepVid websites. Some of these sites do get blocked from time to time or may not be free.
If those methods are not working for you, another option may be Zamzar.
Zamzar takes a little longer but the options are better than most websites for online file conversion. While the choices are better, sometimes the download times are slow. It does take an extra step as a link is sent via email when the conversion has been completed. Sometimes that link comes right away, sometimes it can take much longer if their server is busy. Conversion is free and will handle files up to 100 MB. Once the file is converted, you have 24 hours to download the file (via your email).
VidGod
Zamzar also allows you to take the audio from a video file such as a music video. For this purpose, to make an mp3 file from a .flv file (YouTube), an easier method is to use VidGod. It is an easy tool for stripping the audio from a video. Copy and paste the YouTube URL into the correct box on VidGod, then convert. Conversion is free and very fast.