A bit late to the game, but to save me looking these up again, here are a couple of links with some great explanations on how to use the Google Maps API and the Geocoding functionality:
UPDATE
Nick Tong sent through this link by email, which is specific to UK based Geocoding, however it also contains a wealth of additional information:
UK Geocoding Now Available in the Maps API
July 8, 2007 at 6:11 pm
Another good link for demos etc is: http://www.econym.demon.co.uk/googlemaps/
July 9, 2007 at 11:10 am
Thanks Nick, but that was the first link
August 10, 2008 at 5:52 pm
Thanks for the links, very useful. I made a bmx map with the help of the tutorial. Check it out here: BMX Tracks Map