You can use Google Maps with Google Latitude to track your phone and find it if you loose it or it's stolen. The advantage here is if your phone is turned off or the battery is dead, you can see where it was last time it was on, and have at least some reference to track it with. With the text location apps, the phone must be turned on, and have GPS turned on at that moment for it to work.
Latitude is also good for keeping track of your kids, I don't advocate spying, but if I can't contact them, it's nice to be able to log into iGoogle and see where they are.