I use an iPod touch to watch videos... But most of my 動画 are not ipodの, ipod video format... i searched for video converters.. but the most easiest to use was iTransPod.. あなた can also clip a part of the movie...
iTransPod is a perfect companion for iTunes. It lets あなた import movies, clips, 音楽 動画 to your iPhone, iPod Classic, Nano & 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 (AVM, ASF, WMV, AVS, FLV, MKV, MOV, AVI, 3GP, M4V, MP4, MPG, MPEG, DAT, OGM, VOB, RM, RMVB, TS, TP, IFO, NSV).
あなた can download it here.. link
it also has how-to-use video..