Google Maps saves some map data associated with users. Importing and exporting this map data is generally done using KML, an XML extension for describing geographical data.
Google Maps allows you to create and save your own maps which can be shared with others and edited collaboratively.
It is possible to export saved maps as KML by following these directions.
To import a KML document as a map, first click the "My Maps" link below the main Google maps icon.
Next, click the "Create new map" link: