M.C. Escher's "Ascending and Descending" created entirely in LEGOs. This is extraordinary. I would love to see how they did it. They admit the picture was taken from just the right angle, and it sounds like a small bit of Photoshop'ing to get the perspective point right.
(found this one via Cory at Boing Boing: A Directory of Wonderful Things)
UPDATE: 4:17PM - I was browsing over at Daypop's Top 40 Links and I noticed that the LEGO link is the number 1 link in the weblogger community at the present time. How original I am!