I've been playing around with this neat little piece of software, Blue Marble Viewer. Basically this displays a picture of Planet Earth from any angle you care to choose - like a sort of virtual globe. You can zoom in and see all sorts of details of the surface, from ripples of sand in the desert to pollution in lakes to deforestation in the Amazon rainforest to impact craters to the Great Wall of China and everything in-between. It uses an obscene amount of disk space (about 2Gb uncompressed) and the resolution of the most detailed picture works out at 40960x20480 pixels, which means that each pixel is a little over 1km square at the equator (less at the poles). The overall effect is quite incredible.
The data comes from the Blue Marble section of NASA's Earth Observatory website (which is one of the most awesome sites on the web in my opinion). Another image on that site is a composite of global cloud patterns, which I liked so much I printed it out, framed it and hung it on my kitchen wall. Yet another is the famous "Earth at night" picture which is the desktop wallpaper of one of my computers at work.
I've got BMV compiling and (more or less) running under Windows now, but there are still a number of bugs.
Very geeky fun.