Stellarium - Stellarium is a free open source planetarium for your computer.
SkyView - SkyView is powerful, easy-to-use app that answers questions about stars, constellations, and more.
Solar System Scope - 3D model of the Solar System and night sky in real time
Planetarium - A browser-based virtual planetarium of stars and planets, customizable to any location and time.
KStars - KStars is a Desktop Planetarium for KDE.
SkEye - SkEye is an advanced Planetarium that can also be used as a PUSHTO guide for telescopes.