You can try Movavi Flash Converter, the ideal tool for downloading video from YouTube, Google and other popular video-sharing websites and converting Flash (.flv) videos to any format for any device. step by step guide:
http://blog.flvto.net/watch-youtube-video-on-ipod/
1, click the URL button or select the Add URL command from the File menu.
2.Enter the URL of the YouTube video you wish to download.
3, Select output format and choose right preset.
Output formats: AVI (DivX, XviD, etc), MPEG4 (iPod, MP4), 3GPP (GSM), 3GPP2 (CDMA), QuickTime (MOV), WMV, Flash (FLV), WMA or WAV.
Hope it helps,