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.
Homepage
http://www.stellarium.org/
Downloads
for Linux
http://downloads.sourceforge.net/stellarium/stellarium-0.10.2.tar.gz
for Mac OS X
http://downloads.sourceforge.net/stellarium/stellarium-0.10.2.dmg
for Windows
http://downloads.sourceforge.net/stellarium/stellarium-0.10.2.exe
User's Guide
http://downloads.sourceforge.net/stellarium/stellarium_user_guide-0.10.2-1.pdf
