Google recently announced the new Google Earth Browser Plug-in, which brings the rich mapping and interactivity of the Google Earth application directly into the web browser, "bringing the full power of Google Earth to the web, embeddable within your own we site." And along with the plug-in comes the new Google Earth API (profile).
And besides the API, there's lots of power in using KML, the XML mark-up language for expressing geographic information. Here it lets you easily display data in Google Earth and Google Maps.
The Google Earth API Developer's Guide is the place to start for details on the API. You'll need to understand KML to take full advantage of the API's capabilities. See the Google Earth API Interfaces for a list of object interface declarations.
A great way to see what's possible with the Google Earth API and plug-in is to install the plug-in , then visit the Google Earth API Examples page. The Samples page provides 31 API code snippets, and lets you run the code and view the results. To see KML in action, visit the KML Playground. Want to test your global geographical knowledge? Take the Geo Whiz challenge.
John Hanke, Director, Google Earth and Maps, spoke recently about A new world unfolding, where something that might be termed the "geoweb" will continue to grow and evolve as people "figure out how 'earth browsers,' embedded maps, local search, geo-tagged photos, blogs, the traditional GIS world, wikis, and other user-generated geo content all interrelate."
And with over over 60 mapping-related APIs already, there's surely lots of interesting, valuable geoweb development to come.