Explanations given by Mark Liberman: "you can see the word of your choice spelled out in letters made up of thumbnails of the publications whose titles contain it. (You can also ask to collect the works by authors rather than titles, or use thumbnails from the covers of music CDs or video/DVDs rather than books.)"
As I understand, they use Amazon web services. What a creative use. [ April 19, 2005: Message edited by: Mapraputa Is ]