Here is a video of me and my team (575, in neon yellow shirts) competing in the VEX Robotics World Championship:
We won 2nd Place in the Programming Skills challenge at the World Championship that year.
Here is a video of the autonomous routine I programmed for that challenge. This program used a variety of closed-loop algorithms (some of which are described in RobotC Tips), but is driven primarily by a PID line-following algorithm fed by an array of 5 photoresisters. This setup allows the robot to rapidly follow lines, detect intersections, and turn on intersections.