Each continent is (partially) shown here as seen from a satellite. The images are a "patchwork" of several different satellite images, which explains the lack of clouds. They are all taken at the same hour (noon or close), so there are almost no shadows.
Images taken from UNEP (2003), ISBN 92-807-2272-5 Selected Satellite Images of Our Changing Environment.
Except for the Antarctica and Africa images which are from http://visibleearth.nasa.gov/cgi-bin/viewrecord?11656
Document available online as 13 MB PDF file: http://www.na.unep.net/publications/selected/Selected.pdf
