Stellarium
Stellarium is a free planetarium software, licensed under the terms of GNU GPL, available for Linux/Unix, Windows and Mac OS X. It uses Open GL too render a 3D photo-realistic ski in real time. With stellarium, it's possible to see what your eyes can see, binoculars or a small telescope.
Stellarium should not be used for very high accurate calculation or ephemerids like eclipse predictions. However, it is the ideal program to prepare an observation evening with naked eye, binoculars, or small telescope.
Stellarium is developed by the french programmer Fabien ChÃÂéreau.