I have been experimenting with apps that I can use to produce slideshows to use in my library lessons, I'm going to use this with the Year 4s when I introduce the Dewey Decimal System to them. I usually start by drawing a distinction between fiction and non-fiction and then get them to think of reasons why sorting everything alphabetically might not be the most user-friendly approach- using a 'shelf' of fiction and non'fiction books (three on the same topic- scattered through the shelf when sorted alphabetically) as an example. I'm going to follow this slideshow with the Dewey Decimal Rap, show the kids a few examples to think about and get them to decide which classmark they might go under and 'ta da!' there's a neat little introduction to the DDC. Some of my Yr 4s this year can still sing the Dewey Decimal Rap even though I only showed it to them the once last term!