Line follower is famous basic robotic project. You can use logic gate IC or microcontroller to handle the sensor. But, I prefer MCU for easy control. If you want to learn build robot that can follow a dark line on a light background, check out arduino line follower by DuFFxP93.
The robot uses an Arduino Duemillanove with the AVR ATMega 328 as main processor. Two Parallax Futaba Continuous Rotation Servos are used as driving force. While the sensor uses Pololu QTR-6A IR Reflectance Sensor Array. As power source the project is equipped with 4 rechargeable NiMH Duracell AA Batteries.