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.

Features:

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

interface:
a powerful zoom
time control
multilingual interface
scripting to record and play your own shows
fisheye projection for planetarium domes
spheric mirror projection for your own dome
graphical interface and extensive keyboard control
telescope control

visualisation:
equatorial and azimuthal grids
star twinkling
shooting stars
eclipse simulation
skinnable landscapes, now with spheric panorama projection

customisability:
add your own deep sky objects, landscapes, constellation images, scripts...
[License: Freeware| Requires: Win All | Size: 43.5 MB]