The new 5.0 release now features 3D bathymetry -- you can explore the ocean floor. Depending on the 3D capabilities of your machine, you can even see wave motion on the surface of the water when you tilt your view. Previously, Google Earth sported a 2D relief map of major ocean features, but with 3D ocean view, you'll actually see 3D terrain underwater. Environmental information about the ocean, including fishing and whale migration tracks have also been added.

Historical imagery is new; it enables you to "turn back the clock" to view historical satellite imagery on different locations.

Google Earth's capabilities extend beyond just the planet Earth, too -- you can now view Mars, using the same controls you'd use to navigate around Google Earth. The Mars maps include satellite imagery along with 3D terrain, high-resolution images, and a view of the tracks and locations visited by Mars landers.

HomePage: http://earth.google.com