If you'll be traveling abroad, you may want to register your travels with the State Department at http://travelregistration.state.gov. This automated registration makes sure that the U.S. government has the ability to know that you are in-country should extraordinary circumstances require evacuation of American citizens.
It's a really nice idea. Unfortunately, the site is slow, clunky, and entirely too cumbersome for me to bother with it. I'm sure that I'll wish otherwise if I'm caught in a sudden rebel uprising. In the meantime, if you really, really like typing out the details of your entire trip, you'll be glad to know that the State Department has anticipated your desires and designed a site just for you.