OpenTTD is an open source clone of the Microprose game "Transport Tycoon Deluxe". For more recent versions visit our website: http://www.openttd.org
Old style soccer game with many exciting features
Eat the whistle GPL is a football simulation game written in C that works on many platforms (win32/linux/macosx/amigaos/morphos), it uses the SDL framework. It has a multiplayer internet playing option in alpha stage.