Here’s a post from GeoChalkboard explaining by way of examining a simple application that displays geologic points of interest from around the state of Texas available in an XML file format.
The tutorial highlights the usage of two methods (GXmlHttp and GDownloadUrl) provided by the Google Maps API to read XML files.
Lat long coordinates and information associated with each point of interest are read from the file and markers are generated with location information being displayed via an information window.
If you are just beginning to create Google Map mashups and looking for some simple examples on using XML files and the maps API, check out my previous posts.