I think on of the best is http://vixy.net
Copy the address of the video on youtube (URL) and then go to http://vixy.net and paste the URL there.
You can also choose which format you want to download, either Windows Media, Quicktime, or just download the audio file from the video.
This website is in trial now, so occasionallly, it *may* not work.
good luck
Oh also, if you download in .avi format (as it says its for windows, you would need a plugin called DivX.)
I suggest downloading it in .mov format and use Quicktime player to view the file) it works for windows as well
elevenLoops.
(I previously answered the same question to another user)
(its good to search through previously answered questions before asking one ) :-)