Ascii Sector

Ascii Sector (aka Privateer: Ascii Sector) is a free space combat/exploration/trading game for Windows, Mac OS X and Linux. You start with a simple spaceship and can then accept missions or trade goods to earn enough money to upgrade your ship or buy a new one.

You can engage in deadly fights both in space, on the ground and on board spaceships, and using the Ascii Sector scripting language, you can create your own quests for the game or have fun with other players' quests.