BBC has a fun project, "Dimensions," which allows you to plot various areas and distances against a landscape that's familiar to you. Above, the Mars Spirit rover almost made it to the outskirts of my little burg before becoming mired in a sandtrap on the far side of Witham Hill. The engine is somewhat limited: you can't rotate it, or shift it manually to begin and end in positions that better conform to locations you'd like, but this kind of thing really does help me get a sense of scale of things. For example, I've been reading about the awful flooding in Pakistan, but still hadn't had a gut sense of the area affected...By choosing a location that puts the ends near places with which I'm familiar- in this case, Enterprise, Or, near the Wallowa Mountains- allows me to see that the swath of destruction extends from Calgary, Alberta to near San Francisco. Wow. There are lots of these overlays, filed under various categories. Another fun one is the depth of the Marianas Trench, laid out as a north-south distance.