I just came across a site which converts the youtube videos into mp3 very fast..I mean really really fast. It actually caches the previously converted file. So If you are downloading the file first time then it takes time but if you are downloading popular youtube song( which is probably already been converted and cached), then it is super fast.

Here is the link and enjoy
http://www.youtube-mp3.org/


You can even crawl through the internal code of that website and share the actual link of the cached file.
For example here is link for kathy perry's "teenage dream"
http://www.youtube-mp3.org/get?video_id=98WtmW-lfeE

Enjoy Surfing