Google Earth was only a desktop apps. It is now available online through internet browsers. Google has released a new API for developer, users can download the plugin and browse the 3D world right from Internet Explorer, Firefox and other browsers. There are already some examples you can try out. It will not replace Google Maps because the thing is completely different. Navigation is smooth according to the reviews on internet. Currently, the plugin is only for Windows.

[via O'Relly & Google LatLong]