I will prove to be your best choice when it comes to google maps integration of locations from the database.
Not only marking the locations on the map, I have been doing a lot more stuff in this field, like calculating exect latitude/longitude from postalcodes using geocodes, showing the locations on the maps and their info in popups with pictures and links
Forming group of locations showing them all as one mark on the map and then expanding on a click and so on
pls see links to work and profile in pmb