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.

in version 0.9.0
sky

* default catalogue of over 600,000 stars
* extra catalogues with more than 210 million stars
* asterisms and illustrations of the constellations
* images of nebulae (full Messier catalogue)
* realistic Milky Way
* very realistic atmosphere, sunrise and sunset
* the planets and their satellites

http://www.stellarium.org/