Or should I call it youtube offline? There is a free tool that downloads a youtube video and converts it to a file suitable for playing in a ipod, psp or mobile phone (those are the profiles provided).
I first had the need for it when I saw that there is a video from the Google Developer Days US about Google Gears and Toolkits published in youtube. Nice video, cool stuff, I am sure offline web applications will soon get ubiquitous.
Now I have it on my ipod. Nice.