Stellarium is a free GPL software planetarium. It uses OpenGL to render a realistic sky in real time. With Stellarium, it's possible to see what one can see with the naked eye, binoculars or a small telescope.
Stellarium is developed by the French programmer Fabien Chéreau, who launched the project in the summer of 2001. Other prominent developers include Robert Spearman, Johannes Gajdosik and Johan Meuris, who is responsible for the artwork.