Here's a tip on saving GPS coordinates in Address Book. First, it's lame that GPS coordinates are not a standard field type. Often a mailing address used for GPS will miss the mark by a mile, literally. For some contacts, I use Google Earth to drop a pin on the exact spot, then copy a URL which I save in Address Book.

The URL will look like this:

http://maps.google.com/maps?f=q&q=38.343941,-75.187239%20%28Ocean%20City%20Worship%20Center%29

One quirk is that the URL pastes fine on the iPhone, but on the Mac, Address Book converts those %20 characters to spaces. To get around that, I looked at an export of a contact and noticed we can substitute %2520 for %20, and then Address Book will save it cleanly. The magic is that the URL will fire up Google Maps on the iPhone with a single click.

To make this work, I had to change Google Earth's preferences to default to decimal degrees (though anything beyond 6 decimal places is overkill).

[robg adds: I haven't tested this one.]