In my post about the sites I created with umbraco. On 1 site (www.hizihair.nl) I'm using google-maps to show locations of shops.
There's also another feature: Visitors can put in their postal-code. A script then uses google-maps to lookup the shops that are within a certain distance (a variable the editor can fill in). Try yourself, goto the site, fill in 2132DK in the fill-in top-right and press enter. You'll then get to see the shops within a certain distance from that postal-code, the closest one is top-most one.
Just thought to share, if you want to konw more, drop me a line.