This is one of the best desktop planetarium programs I've ever seen. The 'Google Earth' of the universe, it features some of the best photography I've ever seen of the night sky. The stars move in real time, and your time and position are highly customizable. Check out the view from Toronto, then spin over to Tel Aviv - or even the Moon, for a unique viewing experience. You can even change the terrain! Zoom in to see lifelike pictures of Jupiter's moons, or spin across to Alpha Centurai. The program is full of little touches that make the experience complete, such as the occasional shooting star. Stellarium also features a special projector mode for use in planetariums.

Stellarioum allows you to view the organization of the stars and other objects in the sky based on any time, or location you wish, including views from other planets. With the optional libraries installed it becomes ever more impressive because of the plethora of object that you can view. I often recommend this is a "wow factor" program to introduce open source software to others.