Jumpgate: The Reconstruction Initiative
Jumpgate is an MMO that began in 2001. It's a space flight sim with three factions, a wide variety of ships, and a fairly dynamic economy. It shut down in 2012 but has been brought back to life through the magic of reverse engineering, or something, and is now free.
Choose one of three factions and make your place in the galaxy, via missions, mining, combat and a host of other activities.