Scratch-Off World Map. Scratch of a place whenever you visit it, or use this as a teaching tool. Whenever you teach the students about a place, scratch it off! This could also be used to teach students the locations of different places in the world.
Not only does packing everything in a carry on let you breeze through the airport, but it makes traveling in general so much more pleasurable. No more wardrobe melt-downs. No more lugging around cumbersome items on cobblestone streets.