Oh, believe me, honking and getting mad was always my last resort. I agree that a quick flash of the headlights is good way of politely asking someone to move into the next lane (even though they should know to get over for faster moving traffic).

Also, like I said earlier, I don't get mad if they are taking they're time (at their own speed) to pass any cars on the right. It's when people stay fixed in the left lane that gets to me. I was very polite once, and actually had a guy signal for ME to go around HIM on the right. There wasn't anything wrong with his car, he was just too lazy to get over when there was plenty of space.

It just makes me slow down to *exactly* the speed of the other car

I'd suggest that slowing down when someone is mad at you and driving erratically, just to "teach them a lesson" is probably one of the worst things you can do.