National Gallery of Art
National Gallery of Art: m.c. Escher
An awesome review of the M.C. Escher exhibit at the National Gallery of Art. There are 24 images of Escher's works here out of the 330 that the National Gallery has on hand. There is also a biography on Escher that is very useful.
Mark Harden's Artchive
The Artchive Jasper Johns
This site provides access to 29 images of work by American artist Jasper Johns. Popup ads must be exited before you can see the image.