Link: http://fileforum.betanews.com/detail/Stellarium_for-Windows/1122897455/1

I've linked this before but since then it's got some updates and some of you might not have heard of it -

Stellarium renders 3D photo-realistic skies in real time with OpenGL. It displays stars, constellations, planets, nebulas and others things like ground, landscape, atmosphere, etc.