Ever since I'd been working on various Google Maps hacks I'd been thinking, "Hmmm, I've done Gmail hacks and Gmaps hacks, what could I do that would combine both?".
This page includes some very basic instructions for using an initial rough version of this functionality that only maps US State/Zip codes locations. (The current version is a bookmarklet, but it would be ideal for a GreaseMonkey script--which would solve some issues with the current version.)
To take a look go here.