On Monday evening I was catching up on the previous week's worth of software updates announced at VersionTracker.com
and found a cool desktop utility for Mac OS X (version 10.3 and higher). OSXplanet 1.0
will put a real-time view of the Earth as the desktop picture behind your programs and icons. Select from several map projections and overlay data for clouds, active volcanoes, and recent earthquakes. The program will update the image periodically, so you can watch darkness progress over the Earth as you spend your time working or just watching videos at YouTube.
You're not limited to the Earth, however. You can select other rendered images of the Sun, Moon and planets and even a dwarf planet. I haven't toyed around with many of the options yet I'm happy to have my desktop show a view hovering over Boston (with epicenters).
The program is free, but you can make a donation to the author, Gabriel Otte, a high-school senior in California. It's based on an open-source software project called xplanet.