Pioneer - Pioneer is a space adventure game set in the Milky Way galaxy at the turn of the 31st century.
Space Engine - Space Engine is a realistic virtual Universe you can explore on your computer.
Vega Strike - Vega Strike is an Open Source 3D Action-Space-Sim that lets you trade, fight, and explore in a vast...
Celestia - Real-time 3D visualization of space
X - It is a science fiction space trading and combat simulator series.
Stellarium - Stellarium is a free open source planetarium for your computer.