Are you a busy guy (or gal)? Out and about, running around, nobody knows where you are. You can keep everybody in the loop with Fire Eagle.
Fire Eagle is a free service running under the Yahoo umbrella that lets you update your contacts with your current location. After a free sign up, you can update your physical location through their website or your phone. Let people know your exact location, give out only your city, or operate in stealth mode and don't give 'em anything. Blog on the road and let everybody know where you are. Check in as you backpack across the country.
Fire Eagle is a free service.