here are some options, one or more may work for you:
1. take a hot water shower
2. have a glass of warm milk before you brush your teeth and go to bed
3. listen to music, but preferably something like radio, where you have no control over the REV/FF buttons. or you could put your ipod in shuffle mode, and keep it just out of reach of your hands.
4. turn on cnn headline news at a low volume. after 15-30 min, the news starts looping, and within an hour you'll be bored to death
5. avoid medication at all costs... that's a door you don't wanna open. ever. at the most, have some nyquil, but nothing else.
6. have two to three glasses of red wine. drink it fast like medication, not slow like you would at the dinner table.
7. sourceninja's breathing exercise is good stuff, but it takes a few days before you feel any benifits. if it's too tough, here's an easier way out: sit in a meditation-like pose, breathe in deeply while counting from 1 to 5, then hold your breath as you count from 1 to 5, then release your breath as you count from 1 to 5, then hold your breath as you count from 1 to 5, breathe in ... REPEAT this ten times, all the time concentrating on the bridge of your nose, concentrating on the air you're breathing in and breathing out. if not anything else, this will definitely push your pulse rate down (and maybe your blood pressure too).
8. some people suggested fap fap fap... what the heck, give it a shot, it might tire you out.