YouTube. Well, there's a YouTube like website devoted to Linux! It's called LinuxTube. Folks have been posting and broadcasting videos of their Linux desktops.
Here's a recent example. It's a Mandriva 2008 system doing some amazing things and utilizing its 3D desktop abilities.
LinuxTube is a great site to explore and watch some really slick Linux systems at work. It gives you a great look at jut how powerful and versatile Linux really is. And if you run Vista, you can compare Compiz (the Linux 3D desktop) to Aero.
And yes, there are a lot of Linux videos on YouTube. But LinuxTube gives you channels for each Linux distribution. So, if you want to see videos of only Ubuntu Linux, you can go directly to that channel. It's a real time saver and will certainly help you make a decision of which distro to try. You can view the Linux distro in action before you download the ISO file!
So give Linuxtube a look. Then, get Linux!