I just took a really fun high-speed driver training (N. Andover MA, "In Control"). Their solution to tailgaters:
1) Move over, let him pass, move back. Maintain 3-second rule (minimum 2-seconds).
2) If you can't move over, increase your following distance (between you and the car in front of you) proportionally to the closeness of the tailgater. In an emergency this enables you to begin braking gently at first so the tailgater has time to back off, *then* you can do an emergency stop. You need lots of extra space to do this.
The important thing *not* to do is try to "teach him a lesson." You're not gonna be able to teach him anything. Just stay safe, don't look directly at him, and relax, knowing that you will survive an emergency.