I have been looking through two really useful digital resources lately. One is the Hathi Trust website. They have been digitizing stuff for some time, and the site is now really useful. You can find all sorts of out of print stuff from the 20’s and 30’s (and beyond) and the search features work much better than in Google Books itself. There are also lots of people coming up with collections like Records of the American Colonies that will give you a huge mass of stuff without you having to look for it. Sadly, nobody has done the a collection on the League of Nations stuff that I am interested in.
It is more or less a better front end for Google Books, and it works quite well. This is partially because it is easier to search, has a better interface for reading, and is better integrated with World Cat. It’s still geared more towards English language stuff, but it is a really helpful source.
The other source are the various bibliographies in Oxford Bibliographies. If you are interested in Classical Confucianism would you not want to know what Paul Goldin thinks is the most valuable stuff in the field? John Chaffee on Middle Period China? Kristin Stapleton on Urban Change and Modernity? Alan Baumler on opium? ((Maybe the last one not so much.)) This is a type of scholarship that strikes me as being particularly appropriate for the web, since these are supposed to be updated every year.
Sadly, both of these are subscription sites, meaning that you can get some of the functionality just by logging in, but you need to be associated with a major institution to look at things for free. The world of scholarship is changing, but less slowly than one might wish.