MyTubePlayer will let you download videos from Youtube, Google, Yahoo and MySpace, save it and play it later while you offline.
Just install it, copy and paste the video link into text box. After download click on video title to play it.
Now MyTubePlayer supports playlists and operations with standalone FLV files.
New features were added in this version: full screen mode (just click ESC), automatic detection of the video URLs in IE (IE integration), autoplay mode, always on top mode, player can live in tray now.