The Earth API allows Javascript code to control a plugin that provides Google Earth-like capabilities for your browser. Below you’ll find Google’s “Hello Earth” sample, which is the simplest possible Earth API application. It just instantiates an Earth canvas and allows you to interact with it.
I thought this was a really neat plugin, you can develop games, trivia quizzes and so on with it, and it’s fully programmable in Javascript, from within your browser.
You’ll find additional Earth API examples here.
You need the Earth Plugin for the sample to run. Instructions should appear on the Earth canvas above.