We have a client that ships from multiple warehouses using zones to determine pricing. They maintain the zones in a Goole Maps document. We are creating a front end that clients can enter their address and we'll show them what their shipping options are. We have the client export their zones as a KML file and upload it to their site dashboard and we import the data into a MySQL database and use ST_Contains to find the shipping zone(s) customers are in.
For the details, see this Gist on GitHub.