A few days back we mentioned YouDown that allows you to batch download videos from YouTube. But what if you want to download your whole playlist from YouTube and convert it to Mp3 format, so that you can listen to all your music later on iPod or any other Mp3 Player?
YouTube is the best place to find your favorite music and then add them to your playlist. You can create two types of playlists, public(which is default) and private. YouTube Playlist Converter is a free tool that allows you to download public playlist and then converts them to Mp3 format.
First enter the YouTube username and hit the Refresh button. Now select the playlist you want to download, choose the destination where you want to save the converted files, and hit Convert.
It will then ask you to choose the videos from the playlist that you want to convert. By default all videos in the playlist are checked, but you can uncheck any video if you want.
Now go ahead and click OK and it will start downloading and converting the video right away.
The output would be in Mp3 format which can be later copied to any mp3 player(including iPod and Zune). 
Download YouTube Playlist Converter
It works on Windows XP, Windows Vista, and Windows 7. It requires .NET Framework 3.0 SP1 to be installed. Enjoy!