The latest version of Google Earth continues to set the mapping paradigm. Accessible enough for casual users, Google has added features that make it a necessity for those whose topographic desires are more serious. Although Google Ocean is the big newsmaker in version 5, you can also check out the surface of our nearest neighbor, Mars, as well as incorporating historical Earth maps.
If you'll forgive the pun, the oceanic maps are pretty cool. They provide the capability to plunge to the floor of the sea, view exclusive content from the BBC and National Geographic, and explore shipwrecks like the Titanic in 3D. Exploring the Martian surface is limited to data provided from NASA, but that's not much of a limitation considering that it's unlikely that most of us will ever get to visit the Red Planet. Switching between Google Earth, Sky, and Mars can be done from the menubar or from the planet icon on the toolbar.
Most of the interface's real estate displays a rendering of the globe, which can zoom in on a satellite image of your destination once you've keyed it in. Controls live on a top toolbar and a left-side navigation window that lets you quickly jump between different views and locations. Google's Street View, real-time illumination of the Earth, roads, restaurants, and even crime statistics can be displayed. Smooth integration with Google's 3D rendering program SketchUp means that you can design buildings and see how they'd interact with their surroundings on the fly.
The only downside to the program is that it can consume a large amount of RAM, so older machines might experience performance issues, but even that can now be configured through the Options menu. Everyone else is bound to love Google Earth, both as an entertaining novelty and an informational tool.