We have a client that wants a store locator on their website. I've been asked to find a webservice that will allow us to send a zipcode as a request and have it return locations within x radius. We found this, but it's maintained by a single person, and doesn't look like it gets updated or supported very well. We're looking for something commercial, ideally that updates their zipcode database at least once per quarter, and that has a well-documented API with PHP accessibility. I won't say price isn't an object, but right now we just want some ideas, and my google-fu has failed me. 
Recommend a web service that handles location within a specific radius?
web services