Space Engine - Space Engine is a realistic virtual Universe you can explore on your computer.
Stellarium - Stellarium is a free open source planetarium for your computer.
Celestia - Real-time 3D visualization of space
Sky Guide - A window to the stars has never been more beautiful and easy to use.
SkyView - SkyView is powerful, easy-to-use app that answers questions about stars, constellations, and more.
Gravity WebGL - A gravity simulator, with updated movement controls