Here's the site, but the photos don't load anymore:
Maybe someday the National Archives will get the whole collection of 120,000 Federal ("EAP") historic photos back online again. It was awesome. Fortunately, I had already downloaded a few like these:
From the Kodak Negative File, record group 142, Tennessee Valley Authority, National Archives
A very informative technical paper- http://www.umiacs.umd.edu/~joseph/nara-image-collection.pdf - explains what was involved in getting all those photos online. Why they're gone, I don't know.