My former student Matt Wolodzko tipped me off about this excellent website that shows the scale of the universe, from the very large to the very small: http://htwins.net/scale2/. I recommend it highly for engaging students with the concept of scientific notation.
While I’m on the topic, here are two videos that describe the scale of the universe. The first was a childhood favorite of mine — I vividly remember watching it at the Smithsonian National Air and Space Museum when I was a boy — while the second is more modern.