What a difference a few years can make. A few years ago, folks in the library world (myself included) were arguing about whether it was a good idea to let other people copy and build on their catalog records. Whether or not libraries could or should reuse and redistribute records from WorldCat, for example, was up in the air. Some of us were starting to take small steps towards putting catalog records under open licenses.
50,000 online book and serial catalog records released as CC0
This was one of the first and the best resource I found for locating etexts and I still use it.