ARCE Sphinx Project 1979-1983 Archive
The jewel in the crown of internet resources relating to the Great Sphinx of Giza has to be the ARCE (American Research Center in Egypt) Sphinx Project 1979-1983 Archive . This relatively new resource includes maps, scale drawings and photographs of virtually every inch of the monument recorded in incredible detail. There are photographs in this collection that I can almost guarantee that you will never have seen before, including photographs from the Archives of P. Lacau, one of the few records of the excavations of E. Baraize in the area of the Great Sphinx between 1925 and 1936.
The website is not the easiest to navigate. This link will take you to the main page. On the right hand side of the page there are links to "Data Records" and "Media" which allow you to browse the archive. Alternatively you can type a word into the search box below these links. I'm still finding my way around it.
An unmissable gem is right at the bottom of the main page, where a link is provided to a "digitally remastered" copy of Mark Lehner's 1991 PhD dissertation The Archaeology of an Image: The Great Sphinx of Giza. If you prefer you can go straight to the page hosting the document here. Unlike the copy available on Digital Giza it also includes an indispensable volume of photographic plates some of which belong to the Archives of P.Lacau mentioned above.