Using the Google Static Maps API with a Grid Layer.
A Grid layer with a custom getURL method can be
used to request static maps for a specific extent and zoom
level. The Google Static Maps API is the most reliable way to
get Google base maps in OpenLayers. Note, however, that this is
limited to 1000 page views per viewer per day. Every map center
or zoom level change increases the page view counter by 1.
Look at the google-static.js source to see how this is done.