In today’s New York Times you can find an excellent article on the limitations of digitization of historical sources. I agree that there’s still far too little available online, caused by the twin problems of copyright limitations (particularly for 20th century works) and the sheer expense of digitizing sources.
While the article does depress me with the sheer number of sources unlikely to make it to digitization, I remain a fan of the premise and am always happy to learn of new electronic resources. I read that the Parker Library getting help from the Mellon Foundation to digitize many of its manuscripts: what a boon that will be! In the meantime, you can make do with their beautiful Chronica Maiora of Matthew Paris which is something I’ll share with my students next fall in the late medieval survey course.