Stuart Eve and I have been experimenting with using MapServer to serve WMS layers onto GoogleMaps. We successfully managed to dump out data from MS SQL Server to Shapefile format. This means that data can be bulk uploaded to the database and SHP files can be created by a scheduled task. MapServer then queries the SHP file as part of a Web Mapping Service request from a GoogleMaps interface.
You can read more on the Online Archaeology Blog:
http://www.online-archaeology.co.uk/wordpress/