Via the Bad Astronomer, we have this awesome little sliding scale to give you a perspective of just how small things scientists talk about actually are. This scale goes from a coffee bean down to a carbon atom, which is the coolest thing since the underside of your pillow last night. Yes, I checked.
Going the other way, here's a short video showing the relative sizes of all the planets in our solar system and on up to some damn big stars. There was a video much like this on Phil's site, but I couldn't remember what it was called and my searches turned up empty. I suck. Mea culpa. Enjoy this anyway.