If you’ve ever followed KDE 4 development then you’ve probably heard about Marble. Marble is a virtual globe which displays the earth. So Marble can be used as a nice digital replacement for your desktop globe at home where you can look up places.
But wait! There’s more to it: Actually these days Marble can also display flat maps (thanks to Carlos Licea), can show different “map themes” and can serve as a Qt4-widget as well as an application!