I use Wavelab 7 Essential for that kind of stuff.  

by the way video download helper is awesome .v  here is another firefox extension that skips the step of having to extract from video file:
 
https://addons.mozilla.or...rc=discovery-learnmore

I just found this a couple days ago. it works great! www.youtube-MP3.org.
WSS

 
I like this one 
http://www.listentoyoutube.com
 
Kenny

Thanks everyone, these are some excellent choices to have. I'm adding them to my favorites and will test them out to see which works best for me.
 
@ Westside Steve & Kenny: these sites that only require a URL, have you noticed which bitrate they are converted at? (I think the lowest standard is 128 kBit/s, but do they even convert at higher rates?) 

Mesh
Thanks everyone, these are some excellent choices to have. I'm adding them to my favorites and will test them out to see which works best for me.
 
@ Westside Steve & Kenny: these sites that only require a URL, have you noticed which bitrate they are converted at? (I think the lowest standard is 128 kBit/s, but do they even convert at higher rates?) 

the site i mentioned just allowed me to download my own tune that i had posted as a wave file
(I posted this as non down load able song on sound cloud )
the file I got was a 128 MP3 ….of my tune …well I might as well post it on sound click since they did the conversion for me 
 
Kenny

 
I am using Program4Pc Video Converter Pro to  like MP3 WAV M4A WMA etc.
 
So if you like, then download the free version of Program4Pc Video Converter Pro here from official website:

 
 
 

Loopback on my interface and record with sonar. You could hardwire the Loopback if your interface doesn't have a soft Loopback.

I've tried a couple Mesh but problems with "extras" I didn't want or know I was getting caused me to search around. I like Any Video Converter too because it's easy and coverts about any video type to audio. I love picking out licks I hear in concerts so using it works great for me. You can tweak it in Sonar to use how ever you want. I've been using Transcribe to finish learning whatever catches my attention. I found a Mahavishnu Orchestra concert  with songs I've always liked so that's my most recent use. Much fun! 

Mesh
Thanks Dave & Bapu for the suggestions. :)
 
 
I don't know too much about video quality, but is it true that some of these HD videos on Youtube also have better audio?

If the video is uploaded in HD to YouTube then the bitrate is 196kbps AAC, which is pretty good - better than 196kbps MP3 and certainly way above the paltry 128kbps MP3 which sites like Soundcloud give you.