I've linked to a video that puts the scale of the universe into perspective, but that started with Pluto and worked its way up. Now Newgrounds user Fotoshop has created an awesome interactive flash animation showing the scale of the universe from the very smallest - the Planck scale - to the very largest - the universe itself. It is made entirely out of win. Check it out. Srsly. (Below is just an image of the thing, click here to go to the animation).
(Via James, via Phil Plait).