On this page, we have a reference to the Google Geocoding API:

http://code.google.com/intl/fr-CA/apis/maps/documentation/geocoding/index.html

Based on that, the following should return the XML as described on the page:

http://maps.googleapis.com/maps/api/geocode/xml?address=1600+Amphitheatre+Parkway,+Mountain+View,+CA&sensor=true_or_false

But, I obtain:

<?xml version="1.0" encoding="UTF-8"?>
<GeocodeResponse>
   <status>REQUEST_DENIED</status>
</GeocodeResponse>

Is there somekind of registration somewhere or has this been discountinued?