RoboCom

Build virtual robots and try to wipe out the other robots using all means possible.
http://www.cyty.com/robocom/

AceUplink

Offers information, forums, tutorials, downloads, and links for several robot games.
http://www.aceuplink.com/

Robot Race

A free Robo Rally clone.
http://rr6.sourceforge.net/

BeBits: RobotWar

Features information, screenshots, and download for BeOS.
http://www.bebits.com/app/1792/

Research Projects: Mission Lab

MissionLab takes high-level military-style plans and executes them with teams of real or simulated robotic vehicles.
http://www.cc.gatech.edu/ai/robot-lab/research/MissionLab/

Robot War Competition

Prizes and information regarding the competition at the IIT chapter of the Association for Computing Machinery.
http://www.iit.edu/~acm/robotwar/

Robots and SRobots

Two programming games written in Comal.
http://www.geocities.com/Area51/Crater/8435/robots.htm

JBotRace

A car racing simulator in which the cars are driven by robots. The robots are small programs written in Java and it is the player's task to program the fastest robot.
http://jbotrace.sourceforge.net

BotBattle

Create open-source robots for arena combat using the bot programming language.
http://www.botbattle.com/

BotWarz

A project based on Bot Arena.
http://student.uq.edu.au/~s348521/plasma/botwarz/

Grobots

A programming game in which robots capable of reproducing compete to survive each other's presence. Robots can move, sense, think, eat, reproduce, communicate, fight, and die - all without human intervention. Includes screenshots, documentation, mailing
http://dschudy.tripod.com/grobots/

RoboWars

Requires players to build a robot using C or C++ and then compete against other robots.
http://www.deepnettech.com/robowars.html

VBRobots

Program robots in VBScript or JavaScript and fight them in an arena.
http://www.geocities.com/dtfinch/VBRobots.html

Robocode Face2Face Competition

Robocode one-to-one competition based on direct elimination. Tournaments are held every two weeks.
http://www.geocities.com/albert_pv/

RobotWar3D

Create virtual robots to run in this environment using any Windows language.
http://www.robotwar3d.com/advscripts/home.asp