RoboCup - robotic soccer

RoboCup is a competition with standard rules, separate "leagues" for different-sized robots, and a simulator league. The aim is to promote AI research. The official long-term goal is, "By 2050, develop a team of fully autonomous humaoid robot that can win against the human world champion team in soccer."

RoboCup home page
Hiroaki Kitano
The central source for RoboCup information.

Soccer Server System
Itsuki Noda
The web page of the RoboCup soccer simulator. You can download the software and a users manual, and there's a lot of other information too.