A football manager simulation game. Bygfoot allows you to manage a team by administering players' fitness, stadium capacity and conservation, team formation, team playing style, player hiring and firing, etc. If you are successful you can become a champion. Else you will be fired after some time.
The game is based on "country files" in XML format that you can customise to reflect your own country's leagues. There are also "team definitions" you can write to have the teams you know of play with their actual formations.
Bygfoot is quite mature and has been successfully compiled on several Linux and Unix systems and even on Windows. It should be compatible with any OS where GTK+2, pango, unicode, libc and glib are available.