iTransPod is a perfect companion for iTunes. It lets you import
YouTube Audio Tracks,
Album Artwork to your iPhone, iPad, iPod Classic, iPod Nano, iPod Shuffle, iPod Touch.
This plug-in appears inside iTunes and is extremely simple to use (Watch demo!). It can understand even the most cryptic video formats and codecs
around (AMV, ASF, WMV,FLV, MKV, MOV, AVI, 3GP, M4V, MP4, MPG, MPEG, DAT, OGM, VOB, RM, RMVB, NSV, OGV).