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. In addition to Earth cartography, you can also check out Google Ocean, historical Earth maps, and the surface of one of our closest neighbors, Mars.
The oceanic maps 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 menu bar 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.
The only downside to the program is that it can consume a large amount of RAM, so older machines might experience performance issues. That can be configured through the Options menu, and recent updates have helped address many of these performance issues, with improvements to rendering speed, frame rate, and even launch time.