ZIP / Postal Code + Country to Geo Coordinates

Question

What is the most complete, precise and reliable way to get the coordinates (latitude / longitude) of a given ZIP / Postal Code of a given country? I need to make a lot of reques

Answer 1

Yahoo! GeoPlanet will give you centroid lat/long points for postal codes. They've been reliable in my experience. The API limit is 50,000 requests per day. I'm not sure what their policy on caching results is. I get the impression that if you contact Yahoo!, you can set up an arrangement with a higher request limit, though it may cost some money.

They also let you download a substantial portion of their data under a Creative Commons license, but unfortunately that appears to be limited to the WOEID relationships and country names.