u can try flv downloader, I've been using it for a long time. it is able to save and download any streaming video from youtube,Google Video, Myspace, Metacafe, Dailymotion, iFilm, Music, eVideoShare, StreetFire, etc. off to your computer's hard drive free.
you can google or yahoo "flv downloader' to search for get it
then you can play downloaded youtube video with flv player free whenever you want
the same with that, you can google or yahoo "moyea flv player' to search for get it