Google Earth seems to have taken the world by storm.
Google Earth offers wonderful aerial views of any point on earth, including volcanoes, islands, etc. Navigating through the program is easy and going from one place to another seems like a helicopter ride. Moreover, program displays high-resolution images for major cities like New York, Beijing, etc (you can even see the house!).
More details: http://earth.google.com/sites/
According to their website, the images are photographs taken by satellites and aircraft sometime in the last three years.
Google Earth is simply excellent PR. However, it does raise some interesting questions, such as the cost of the bandwidth and well, cost for getting the images, etc. Currently, Google has integrated search (works for US and some other countries only) in Google Earth. Hence, to cover the costs, will Google include ads, travel booking features, etc in future versions of Google Earth? Remember, nothing is ever free.
If you don't like to download the 10 MB installation file, you can also get some images at
http://maps.google.com (but you will miss out the cool stuff like 3D [see above]).