If I ever teach a robotics class, I'm definitely not giving them a line follower as a project. It's gotten to the point where if you type "line follower robot" or "line follower schematic" or any such thing into Google you get 500 plans for line following robots, complete with diagrams. Speaking of which, OP, Google it and you'll find complete schematics galore. Actually norlin just said that, and he suggested the same book that I was going to. So I'll just second that, I've read it, it's an extremely complete book, it gives you everything from the circuit diagrams to tips on soldering and joining wires and building the frame, to suggested suppliers for the parts.