Heavens Above - Website for tracking Satellites, Space ships and other space objects.
EVE Online - Player-created empires, player-driven markets, and endless ways to embark on your personal sci-fi adventure.
See A Satellite Tonight - Free web app to explore satellite locations.
Elite Dangerous - Elite Dangerous is a 2015 Trading, Action, Sci-fi, Exploration, Open World and Space Simulation by Frontier Developments.
Celestia - Real-time 3D visualization of space
Star Conflict - Star Conflict is a free MMO action game and space simulator that was introduced in 2012.