Postcoder uses the awesome ordnance survey OpenData products to create a fully featured API. The API accepts a full or partial postcode and responds with the closest matches (up to 20 results). It also includes the streets most local to the central point of the postcode called. We've also included a local travel listing with local stations, metros and bus stops included in the feed.
Postcoder has had all of the data converted from the UK Grid system to latitude and longitude values making your intergration into other services such as Google Maps easier and more fluid.