YouTube

Doing a simple search for library, I came across the Cookie Monster - No Cookies in the Library clip. I remember it from when I was a kid watching Sesame Street and I think its a bit of a classic...
There is so much information in YouTube it can be a bit daunting to search. However, I can see its uses when creating interesting Youth and Children's programs for the library. It's also a good place for storing informative videos about the library, such as library tours.
The biggest issue I have relating to the use of YouTube for library related purposes is that of privacy. You would have to be very careful of what was posted, to ensure that everyone involved in the clip was happy for the film to go on to the Internet.