What you are looking for is called Geocoding.
Google provides a Geocoding Web Service which should do what you're looking for. You will be able to do geocoding on your server.
JSON Example:
http://maps.google.com/maps/api/geocode/json?address=1600+Amphitheatre+Parkway,+Mountain+View,+CA
XML Example:
http://maps.google.com/maps/api/geocode/xml?address=1600+Amphitheatre+Parkway,+Mountain+View,+CA
Edit:
Please note that this is now a deprecated method and you must provide your own Google API key to access this data.