Does anyone know of a good (inexpesive or open source) store locator script?

I would like it to be one that will allow users to register and list their store, and then customers can come by and search for a store using city, state, or zip code.

An example of what I need is here, http://www.pethobbyist.com/locator/ But I dont need one as graphical. If it can link to mapquest though, that is a plus.

I have also read that these arent hard to create, but I wouldnt know where to start. If anyone can help me out or make a recomendation on a readily available script, it will be greatly apreciated. Thanks!