I needed to get a google map to center and scale based on the added points.

I found a tutorial here: http://econym.googlepages.com/basic14.htm

This gave me exactly what I needed.

In short, given a GMap2 object called map and a map of locations (name -> object with lat and lng properties):

map.setCenter(new GLatLng(0,0),0);

var bounds = new GLatLngBounds();

for (name in locs) {
    var loc = locs[name];
    var latlng = new GLatLng(loc.lat, loc.lng);
    var marker = new GMarker(latlng);

    bounds.extend(latlng);

    map.addOverlay(marker);
}

map.setZoom(map.getBoundsZoomLevel(bounds));

map.setCenter(bounds.getCenter());