The Ica-Nazca civilization drew many lines and figures believed to be homage to their gods, now known as the Nazca lines.
For more information on Ica-Nazca line drawings, see here.
Possibly more famous, and much more to my taste, is the Uffington White Horse. See here for more information.
See here for a slideshow of some awesome giant drawings/advertisements made in recent times.
I Drew Something : song, Breaking Glass, artist: David Bowie, album: Low