Nowadays there`s no need to have to watch videos from the famous YouTube directly on the Internet, as with programs like Elltube you can download them directly to your hard drive and then watch them as often as you like without being connected to the Internet.
Elltube lets you download videos in both the original FLV, and in AVI or MP4. If what you are interested in is the audio from the video, you can rip that audio and save it in MP3 or AMR formats. You can even make graphic captures of the video.
Elltube is also totally free.