Youtube has finally hit mobile phones and is named Mobile Youtube which can be found by tapping in m.youtube.com in to your 3G browser. When you first get to that address you are recommended to buy an unlimited plan as data charges could be high with a service running like this.
Gizmodo put together a demonstration which is linked to after the jump. However, if you want to test it out without using a mobile phone then just go to m.youtube.com in your browser to see what is available. You will get an error when trying to load videos through this method, but it will show you what the mobile interface looks like.
One cool thing is that you can see even smaller thumbnails of the videos and skip through different sections such as newly added.