We have built an effective store finder for online retailers with stores using Google Maps.
This means visitors can locate nearest stockists via the map, via searches (by town or post code, partial or full) as well as getting directions - plus all the other good things that Google Maps offers. (See the example of Ness Clothing)
Website managers can upload a table of stores (with an associated image), together with their location co-ordinates, address, phone, opening times and facilities.
Google does the rest.