You learn something everyday. I've been asked to create a distributor feature of and was beginning to wonder where on earth you would start. I wanted to tie it in with the Google Maps API and do some fancy Web2.0 UI stuff. Well after a bit of searching I started to read about the Haversine formula on the Wiki.

Now I'll admit I'm not the greatest at maths, but it lead me onto some more searches and eventually this article on Google. Brilliant, this is an excellent starting point ! Having never created a store locator before I'm going to append notes to this article based on my findings so anyone else happening across this on the internet will know what to do !