TidBITS has a great how-to article on the new feature in iPhone 3.0, called Find My iPhone, that lets you locate your iPhone. This feature requires a MobileMe account, which costs $99 per year (and which I recommend), but there's no other cost. (MobileMe constantly syncs your computer and your iPhone in the background automatically. You no longer need to use iTunes to do it.) If you misplace your iPhone, or if someone has taken it, Find My iPhone helps get it back. You can have it emit a sound, or you can locate it on a map. And more. If all else fails, you can wipe the contents remotely. MacWorld has a post about a couple guys who used this feature to chase down a stolen iPhone. CNet is reporting, however, that savvy thieves can easily disable this feature, unfortunately.