I have to be honest, I hadn't ever heard of mash ups before. I think they are a cool idea, but are one of those ideas that seems so simple you think to yourself.."why didn't I think of that!" I really like the mash up bookr. It would be neat to have the kids write a class story and illustrate it with pictures from Flickr. You could also create a Flickr account, and create an online scrapbook of your year in the library; People could add commments, you could add pictures and use the Bookr feature to explain the events and pictures.