Google Maps Geocoding - JS API V3

All you need is Lat + Lng to add markers if you need to, you can then add a marker to the map using the following. (You don't need to geocode then)

var Latlng = new google.maps.LatLng(myLatitude, myLongitude);
var myOptions = {
     zoom: 12,
     center:Latlng,
     mapTypeId: google.maps.MapTypeId.ROADMAP
};            
var map = new google.maps.Map(document.getElementById("GoogleMapContainer"), myOptions);            
map.setCenter(Latlng);
var myMarker = new google.maps.Marker({
                position: Latlng,
                map: map,
                title: "Your Location"
});
var info = new google.maps.InfoWindow;
info.setContent("<strong>Some Content</strong><br />Some other Content");
info.open(map, myMarker);

So I would imagine you would need a web service or something to pull a list of Latlngs + Address info to populate more markers from your database.
This is how I do it for some of my sites, the user enters the location of some stores or whatever and some content and I pull it out and create the markers.