GoogleFill is a plug-in for the Mac OSX address book that will automatically fill in a US address based on the phone number using a google reverse search.
What does this do?
It's actually harder to explain than to actually show it..I own a Treo 650 cell phone... Great phone and one of the features it has is when you dial a number not in the address book it says "Do you want to add this number?"
So I end up with lots of numbers in my cell phone address book without any corresponding information (e.g. who it is, where they are from, etc.). GoogleFill is my solution to the problem.