NASA's Goddard Space Flight Center has posted pictures of what it describes as the best-ever photos of Earth, on a project called "Blue Marble Next Generation." The globe is assembled from a mosaic of satellite data taken mostly from a sensor called the Moderate Resolution Imaging Spectroradiometer (MODIS) that flies aboard NASA's Terra and Aqua satellites. Details as small as 1600 feet across can be seen.
Earth in high definition and living color (Discovery News)
Blue Marble Next Generation / NASA Earth Observatory (includes links to images and animations)