Many are talking about how Google Maps integrated Keyhole (which they acquired about four months ago) to offer nifty satellite images. For example, here's a top-down view of Amazon HQ in Seattle.
Just like others have offered maps before, others have offered satellite and aerial photos. But Google has combined this with a snazzy interface that lets you do things like click and drag the viewpoint around while the images refreshes dynamically.
Chris Sherman at Search Engine Watch has a particularly thorough review of the new service.