Earthscape provides you the ability to view the entire world on their virtual globe. This app uses satellite imagery to show you some of the closest possible pictures in the United States and some pretty decent ones worldwide. Earthscape also allows you to tag pictures to your location and show you pictures tagged by others so you can get a better idea of what's going on where.
Earthscape is very similar to Google Earth, but is the first client of its kind for the iPhone. You can actually zoom all the way out to world view and spin the globe around. Pick anywhere you want to see and double tap or push your two fingers apart to get a more zoomed in view. In the U.S. you can actually see the houses and roads very well. In other countries you don't have quite as clear of a view due to Earthscape not having the rights to those images yet.
Pressing the locate button will zoom in on where you are with pretty decent accuracy. What's really enjoyable is that you can switch your view from straight down to something similar to street view. The only difference being that the images are 2D and below you, but you can still see where everything is in relationship to where you position your view.
Tagging images gives you a bit more longevity with this app if you're the type to want to show off cool locations or find cool things randomly. Overall, this is more of a novelty then a useful app. This may be one of those apps that you'll want to show people when they ask what the iPhone can do, but I wouldn't count on using this a ton in your spare time.