One of the best space simulation is available also in a Linux version.
Thirty-two years have passed since the Great war. Terrans and Vasudans have formed a new alliance. But new threats are lurking around.
Netrek is a 16-player two-dimensional graphical real-time battle simulation with a Star Trek theme. A game is divided into two teams of 8 players (or fewer), who dogfight each other and attempt to conquer each other's planets.
Chess for mobile OS Android, it is possible to play online on FICS, tha largest chess server, or offline against a chess engine with difficulty setting.
Phalanx is a chess playing engine with agresive playing style. It does not have its own graphical interface, but can be used with general chess interface Xboard (Winboard) by Timm Mann. There is also a commercial version that runs as a native Fritz module and thus can be used with the Fritz graphical interface.