From Bad Cat Films:
Where I'm At is the handy app that allows you to let your friends know where you are with just a few taps on your iPhone.
Launch Where I'm At and it starts querying the GPS built in to your iPhone. It displays a map of your current location and automatically determines the closest street address. You may then send this information via email or SMS. You can also load the data into the iPhone's copy buffer and paste it into any iPhone app such as Facebook or MySpace Mobile.
The message sent can include a link to a Google map pin-pointing your exact location which then can be used to generate directions to you. Or if you prefer, the street address can be sent.