Well, even I have been using Youtube for quite some time now. I've already developed a taste for a few particular channels. One of them would be the infamous TimeLordfromHell.
A Doctor Who fan living in England, this guy often posts his own episodes and parodies of said TV show. He also hosts numerous original skits and video blogs. Here is one of my favorites:
As for library applications, we could always use it to embed instructional videos. Not exactly sure what we would be needing to instruct patrons online for, but if we did we could use Youtube.