The “Nietz Old Textbook Collection” is a full-text collection with digital editions of 140 schoolbooks and two surveys of historic schoolbooks by John Nietz available at:
http://digital.library.pitt.edu/nietz/
The collection is primarily nineteenth century textbooks however there are secondary sources and search tools located at the site. I also felt the site would be of interest to many others.
(Sent by David J. Roof)