For those that are interested in Astronomy, Celestia is a brilliant piece of software. With it, you can explore the entire known universe, and visit other planets, stars or galaxies. You can travel back and forth in time, for example if you want to reenact a solar eclipse that you missed out on, or would like to see what the next sunrise looks like from the International Space Station. 
Celestia containes detailed graphics of the surfaces on all planets, to the best of our knowledge at the current time. You can move around all objects, and observe tham from wherever you'd like, whenever you like. There are also a large crowd of users who participate to the project and create their own models that can be downloaded and added to your "universe", if you for instance like to add a space probe and see exactly where it is right now.
Celestia is a excelent piece of software if you are teaching astronomy. It makes it a lot easier to understand the overwhealming distanses out in the universe, if you see them with this program. And it is both quick and easy to create images and videos from outer space, like the image in this article. This image show Jupiter with its moon Europa in the foreground.