YouTube launched a mobile interface available at m.youtube.com. To use it, you need a mobile phone that plays streaming videos (RTSP/3GP with H263/AMR) and an unlimited data plan because "YouTube Mobile is a data intensive application."
Most 3G phones support 3GP, but you can also play these files on your computer if you have a player like MPlayer, VLC, RealPlayer or Quicktime.
Only a small part of YouTube's videos are available in the mobile version and that includes short videos that were recently uploaded or popular. There are also three special categories: people, entertainment and "grab bag" and a search box that lets you find videos.
Source:→ Google Operating SystemYouTube, Mobile Phone, Mobile Interface, Online Video, YouTube Mobile, Launched