Slime Volley 2.4Free
Slime Volley is a game inspired by the Java games of the same name (in the style of Blobby Volley).
It is a photo-realistic volleyball simulation : You control a semi-circular blob on which the ball bounces.
A this time, the stable 2.4 version allows from 2 to 6 players, with any combination of local, remote and AI players.
This game is programmed in C with the Simple DirectMedia Library (SDL) libraries, and is available under GPLv3. So it is free (as in beer) and free (as in speech).
Slime Volley is developed under Linux et Mac OS X, and also works under Windows.