Stellarium is a free open source planetarium for your computer. It shows a realistic sky in 3D, just like what you see with the naked eye, binoculars or a telescope. It is being used in planetarium projectors. Just set your coordinates and go.
default catalogue of over 600,000 stars
extra catalogues with more than 210 million stars
asterisms and illustrations of the constellations
constellations for twelve different cultures
images of nebulae .....