First, if you don't have one, you will need to get an API Key here .
Then all you have to do is an CFHTTP call like the following:
http://maps.google.com/maps/geo?q=#yourAddress#&output=xml&oe=utf8\&sensor=true_or_false&key=#yourKey#
Note that the OUTPUT parameter can be also JSON.
And one more note. When processing the result be sure to check the kml.Response.Status.code node that has to be 200.
http://code.google.com/apis/maps/documentation/geocoding/