you have to use the Google Maps API, which is in fact just a set of JavaScript functions. You just have to pass the coordinates stores somewhere in the database from server-side to JavaScript. Here is the code:
<script type="text/javascript">
var map;
function initialize() {
if (GBrowserIsCompatible()) {
map = new GMap2(document.getElementById("map"));
var lat = <asp:literal id="ltrLat" runat="server" xmlns:asp="#unknown" />;
var lng = <asp:literal id="ltrLng" runat="server" xmlns:asp="#unknown" />;
var center = new GLatLng(lat, lng);
map.setCenter(center, 10);
map.setUIToDefault();
var marker = new GMarker(center);
map.addOverlay(marker);
marker.openInfoWindow("Here");
}
}
</script>