youtube converting in Linux?

[Kyle]

Probably the best solution for now is youtube-dl. It should be available 
from your distro of choice. If not, you can find it at
http://rg3.github.com/youtube-dl
You can then use mplayer to dump the audio stream directly from the 
file, or convert it to the format you like using ffmpeg. I have a bit 
more complicated way of doing things that involves getting their new 
WebM videos and pulling out the Vorbis audio using mkvextract, but that 
involves picking through the HTML5 source and doing some creative 
searching and replacing to get the correct link. At this point, 
youtube-dl is still the better option for heavy use. I'm also in contact 
with the developer of Youtube-dl to try to get it downloading the new 
format so that you will always get good audio without conversion if it's 
available, and soon all their videos will be available in this new WebM 
format, which will make audio extraction extremely easy.
~Kyle