I found this page at the MobileRead Wiki:
https://wiki.mobileread.com/wiki/OPDS..._OPDS_Catalogs
Is this it right now? I'm not complaining. Internet Archive and Project Gutenberg have nearly every major out-of-copyright book in existence, but I was hoping maybe there were more out there for more specialized reading. I know
Mantano came with one I didn't see mentioned. It's a science library:
arXiv
http://arXiv.opds.heroku.com/catalog.atom
What else we got?