Incredible map, made using GPS data from Foursquare. The big white light in Mexico City is 50% check-ins from my brother.
This is really beautiful: select a country, and it visually shows you its relationships with other countries, quantified via Facebook's gigantic data set.
Very nice utility to help you visualize what's taking up space in your hard drive. If you are running low on space, use this before you start deleting 1 KB large files.