A Screengang project.
I developed a state-of-the-art shop finder in 2011 using the Google Maps API (application programming interface), database, a custom MODX module and AJAX. It's got all the usual bells and whistles you've come to expect nowadays: No page reloading, search by any criteria (ZIP code, city...), narrowing down by radius etc.
Address management is done via custom CMS module, as user-friendly and easy as it gets. Also, the system recognizes wrong or incomplete addresses, and lets the admin know accordingly, to avoid embarrassing error messages in the live site.