A very nice yahtzee game where you can play against humans or against the computer (including several different opponents). You can find it here. You can find a slightly different version of this program (probably an older version) called yahtzee-sbi which requires a non standard 80×25 display (see here). Another version without colors can be found here.
In order to compile it, I had to edit the file called main.c and replace the line:
I had also to add the following line at the beginning of the file (after the include statements):
void abort(char *msg);