well I've just spent some time browsing Flickr. This site wasn't new to me, I used it a couple of times last year to share photos with my family and friends while we were living in Ayers Rock. It is a great way for people to see your photos quickly and without having to be physically with them. I did find that it took a long time to load the photos so that put me off a bit.
As for library applications, I'm really not sure about this. I'm not a big photo person so I can't really think of how it could be used. Maybe as a way to share photos of library promotional activties - Lib Techs could use it to share photos of displays they've put together to give each other ideas. Still can't think of a way we could use it with our students though.