All of us know this very useful service of Google Maps. And lot of programmers already triev Google Maps API v3. Somebody even met the problem with the limit of the geo coding requests per time period. In some case server-side scrip can help to solve the problem. If the number of the locations is less than 12.000 (monthly limit of requests per IP), you can do geocoding server side and save the results to the database. If your application requires more geocoding requests than you should implement some sort of client-side geo coding strategy. This will use IPs of your site visitors.
As usual I have prepared some code. Right now that is php class that implements server-side strategy of geocoding as a wrapper for the http requests to Google Maps service.
Read complete article: PHP geocoding with Google Maps API v3