Most of our day-to-day experience involves objects that range in size between a millimeter up to a few hundred meters (a large building). But the universe we inhabit has much much larger and smaller scales. It's hard to comprehend just how tiny a bacteria is compared to the size of the solar system.
Universcale is an interactive flash app that allows you to scroll through scales from a proton all the way up to visible universe. The scale contains silhouettes of objects of various sizes. You can click on each item to get more details. This app was made by Nikon (the camera/optics company) as part of the "Feel Nikon" section of their website.
Universcale reminds me of the popular 1977 documentary Powers of 10. But the interactivity of Universcale makes it much more compelling than the documentary.