A couple of days ago I started to clean up my laptop and found a whole folder full of software I wrote for the Botnia RoboCup Small Size Leage team (http://robotics.puv.fi). While most of the stuff is not very useful outside the team, I did find a simulator which was used principally to test the RRT algorithm for path planning, but also to test some basic strategies and as a teaching aid in a course on Object Oriented Programming.
I cleaned it up a little and just put it up on my Github repo, should you be interested. It's written in Java and has a couple of features to play with. You can position the ball and individual robots and it's easy to add small 'strategies'. By default one robot will try to score in a goal protected by a goalkeeper and two defenders. The ball physics are pretty flakey though...
This brought back some memories of all the competitons we participated in and the fun we had building autonomous soccer playing robots :-) The picture below is from the German Open in 2007.