CGFA
Carol Gerten Fine Arts: M. C. Escher
This resource provides a very informative biography as well as a gallery with 15 pictures of great Escher art.
Other
What Is an Original Print?
This site has descriptions of many printmaking processes as well as links to other printmaking sites and galleries.
Smithsonian Institution
Smithsonian American Art Museum: Elbridge Kingsley
As part of the Smithsonian Art Museum's database of artists, Elbridge Kingsley is described here along with information on his contributions to art through wood engraving. Several examples are provided of Kinglsey's wood engravings.