OpenLibrary and its cookbooks
Some of these are available as simple ebooks to download, some newer works have to be "borrowed". But browsing through I see Bittman Bourdain, Reichl, McGee, as well as some very old classics (there's even a timeline at the bottom where you can pick works from a particular year, dating back to the 1400s). This is a beautiful thing.
I spoke too soon on the newer books, it seems. Many of them are actually only available through physical loans. Poo.